The hydraulic wheel motors turn the wheels while unloaded, but slows down and stops when load is applied. The service manual says "check planetary wheel drive to be sure engaging disc is not positioned in freewheeling." So my question is what is the planetary wheel drive, and where is the planetary the planetary wheel drive? is it inside the hydraulic drive motor? Do I have to take the hydraulic motor apart?
And is it possible that this brake cylinder might be engaging when the load is applied?
Well, I just learned that the above picture is not a brake cylinder, it is the two speed position cylinder. So I am wondering if I disconnect it by removing the cotter pin if that will leave the drive motor in low speed which should give the wheels more torque? Just wondering if the Drive motor may have been stuck in high speed, which would have given the wheels less torque?
So I disconnected the two speed shift cylinder, see picture attached, and now the right drive wheel has more torque and turns under load, but the left wheel still does not turn under load. I tried to toggle the shift lever on the hydraulic drive motor with my hand to see if I could get it to change gears manually, but was unable to move it by hand or pushing on it with a pipe. And the two wheel motors shift levers are connected by a long rod. Any thoughts?
An opinion please on the attached screenshot of the drive motor diagram. It looks like there is an internal spring on the main shaft rod that keeps the gears locked into one position unless the lever is moved from 4 degrees to 17 degrees with with a lever that is attached to the two two-speed hydraulic cylinder outside of the motor to compress the spring and engage the alternate drive speed. My question is, what is the default speed of the motor if the 2 speed hydraulic cylinder is disconnected from the spring compression lever, is it the low speed or high speed? And if it is the low speed, I'm wondering why the left side motor did not engage low speed since the two motors spring compression levers are connected by 1 long rod? Broken internal spring on the left side motor? Or just jammed up somehow?
You're not shifting gears with that lever but changing the displacement of the motor. More angle (past center)= more displacement = more fluid required per rev = more torque. There is a small drain line on the side of the motor, remove that when the motors are stalled out. Whichever one has more flow under load will be a bigger problem than the other
Thanks Mike. So should I open both of the drain holes on the left and right motor at the same time and compare the flow that way, or just open one at a time? Not sure what you mean by stalled out. If the drain hole is open, does that mean the wheel will not turn while the drain hole is open?
Mike, actually I could not find any drain plugs on either wheel motor, even though the attached diagram shows a 9/16-18 sae drain port? Unless the drain port is supposed to have a hose attached to it like the smaller hose in the attached picture?
Yes the drain port runs back to tank
Thanks Mike. So I ran each drain line to separate buckets and engaged the drive wheels for 5 seconds. The right wheel spun without getting traction and the left wheel stopped. The right drain line produced 200cc of fluid and the left one 175cc. I then completely blocked off the right side motor but the left side motor still stopped after about 2 seconds. So now I am considering just pulling the left side motor off and disassembling for inspection to see if I can find any broken or worn out parts.
If the motors are plumbed in parallel the one that breaks loose first will get all the flow.
Not sure what you mean by breaks loose. Does that mean that the wheel that keeps spinning when the other one stops is the wheel that will get more flow?
They're spinning on muddy ground or you have them in the air? TBH since the leakage rates are the same I dont think your problem is in the motors
Thanks Mike. When I had both of the wheels jacked up in the air, they would both spin normally. But when I lowered them to the ground, which was soft, they would go forwards or backwards about 6 or 8 in and the left wheel would stop but the right wheel would keep spinning, but not get traction and gradually digging a little deeper into the ground the longer it was engaged. FYI, I disassembled the left motor to inspect for damage and wear, and found none. So I put it back together and I am going to switch the left and right motors to see if right side behaves the same. They are behaving kind of like a car with posi traction in the sand or mud where just one wheel spins. I'm wondering which angle 4 degrees or 17 degrees on the swash plates would give the wheels more torque? I also discovered that there could have been a difference in swashplate angles in both Motors because there was a broken roll pin connecting the two speed shift selector cylinder, which created a lot of free play in the connecting lever. See attached picture.
Okay, so I've been delayed a couple months with this wet weather LOL. So I found no problems with the motors and I reinstalled them only I switched the left and right motors, and the same Wheels were showing the same traction and torque. So then I capped off the lines to the right side motor to see if that would put more pressure or volume to the left side motor, but there was no change in the left side motor motor performance. So now I suspect a problem in the valve manifold, like maybe a clogged filter or broken spring or maybe it's just out of adjustment for the left side motor lines? I'm wondering if these strange looking hex nuts with the Allen screws in the middle pictured are perhaps some kind of volume control adjustment?
the tower looking things with adjustments on top looks like counterbalance valves, they are in the same block with parking break releasing shuttle valve and flow divider according to diagram showed in previous Thread Flow divider is a device which cut the flow to free wheel when you blocked the other. It’s supposed to do that. I’m not clear what kind of problems you having now?
Compare the angles of swash plate lever on both motors at the same position of speed cylinder. Is the connecting rod bent or miss adjusted?
Originally the connecting rod between the swash levers was out of adjustment, but I fixed that and both of the levers are in the fully tilted 17 degree positions, and the rod Is not bent. I just want to see both of the two wheel drive Wheels spinning even if they fail to get traction. Right now just the right wheel will continue to spin. I'm not sure I understand your comment about the flow divider. If I have the right side motor capped off, will the flow divider give more pressure and fluid volume to the left side motor? The service manual did not show the individual internal components of the manifold.
Like I said in the original thread - that flow divider is mislabeled, it’s a typo. So I can’t tell you how it works. I don’t think it is gear divider, but gear one will stop everything if it not getting flow because it’s literally two gear pumps on the same shaft.
I suggest you take the names and terms I used above, google them, find out how components work and what are the symbols for them. It will help you understand things better and faster!
I don’t know what was the reason to install that flow divider on steerable vehicle - but it is acts like locked mechanical differential! And I don’t see any diverter valves in diagram to ingage or disingage!
Thanks so much TVA! I actually bought that Brendan Casey Hydraulics book and it has a lot of symbols and explanations. And thanks for reminding me on that flow divider miss label. I'll be sure to mark that on my hard copy. I think my next step is going to be to do with that manifold what I did with the hydraulic motors, just take them completely apart to see how they work LOL. And I will count the number of thread turns on the nuts and Allen's as I take them out. Thanks again so much for your quick responses!
If that flow divider is a sool type ( most likely) look for scratches on spool or bore. Looks like they wanted to label it as proportional flow divider but forgot to put diagonal arrows across orifices! Also look for plugged pilot passeges.
Wow, great advice! But if they were proportional flow dividers, wouldn't they have to be controlled electronically with some wires going to them?
Proportional means not only ON or OFF but infinitely variable, it can be controlled in many ways, mechanically, hydraulically, ( pilot circuit), electrically, electric over hydraulic, etc.
Hello TVA. So I am taking the manifold apart and a couple of questions. Is this the counterbalance valve in the picture with the spring? Between the piston and the Allen screw was a darker looking oil almost like motor oil, unlike the red transmission fluid and the hydraulic lines and some debris like sand and rust, and I had to tap the Piston out with a screwdriver because it seemed to be a little jammed, and there looked like a little surface corrosion between the piston and the Allen screw on the cylinder wall. So Dremel tooled wire brush the inside of the cylinder and now I can move the piston with my finger up and down. It looks like the purpose of the Allen screw is 2 compress the spring, so would this adjustment be to allow more or less flow of hydraulic oil going to the hydraulic motor? And my second question is since you recommended blowing out the manifold with compressed air, how important is it to remove the Allen screws like the one pictured with the Allen wrench and the other screw in plugs like the one pictured with the screwdriver pointing to it in order to blow out the manifold with compressed air? I ask this because please Allen screws and screw in plugs are really tight and may take an impactor to remove them. And my third question is what is the purpose of the Allen screws in the manifold block? It seems like there is one Allen screw for every two large hoses entering the manifold. Are they bleeder screws?
The tower looking things looks like the half of something like relief or counterbalance valve, the spring supposed to push the spool. Doesn’t look like it is cartridge, so spool is riding inside of the blocks body or there’s could be another sleeve pressed in to the body. The Allen plugs probably diagnostic test ports, or technological opening if it has some components behind it. Without exploded view or illustration some kind, or having it in my hands to do a “reverse engineering” it’s hard to say. See if there’s a spool behind that large hex plug, if there’s a spool with smaller diameters at the ends and larger in the middle - that’s your flow divider. Take everything apart, carefully photograph and document as you go, to correctly assemble it back together. Post more pictures - and we will try to figure it out together.
I would recommend to replace the O rings on the piston with Duro 90 ( for dynamic application) O-rings. Got to measure grove to select right size. The oil behind the piston is a trapped oil that got behind the piston. That piston is just puts tension on the spring - so it’s not supposed to move unless springs tension gets adjusted!
In the fourth picture to the right of the Allen wrench is the hole where the tower hex nut and spring came out of. Manifold case appears to be cast as one piece and does not split apart. So could the spool you are talking about be inside this one cast piece? And if so, how would I get it out to inspect? So one end of the spring contacts the piston and the other end of the spring is contacting that area around the small hole in the manifold body. Should I be able to press that end towards the manifold body with a screwdriver? Is there another spring inside the manifold body around the spool? I Googled imaged hydraulic spool, but not seeing what I'm looking at.
There should not be another spring under counterbalance valve spool, spool should be two sections, one section should have three times smaller effective area. There should be another passage coming through manifolds body, beside big one connected to port ( hose ) hole. You can use needle nose pliers to pull things out, or try to carefully blow compressed air to pop things out.
Okay thanks much! I will work on that. Should I go ahead and try to get those large screws out like what the screwdriver is pointing to in the third picture? Is it okay to use an impactor for that?
Yes use impact, it’s probably hung up on aluminum washer or rubber O-ring pretty good. The only thing - before using impact put things back together or remove all loose components and put them aside, to prevent things flying out and loosing them or not knowing how they supposed to be.
Wow, I used the needle nose like you said to lift the spool out, and it just came right out! And now I also see that at the other end of the spool that there is a large screw but I was asking about using the impactor on. So I'm guessing that once I get that screw off there will be something else that will come out of that end? Oh and also in the picture, you will see some large bits of metal shaving like perhaps from some other component in the hydraulic system that came apart and metal shavings got passed in the hydraulic lines to this manifold?. So that may have been blocking the spool from sliding in and out and thus restricting hydraulic fluid flow to that hydraulic motor on the right side?
Okay, here is a picture of a plunger looking type piece that came from the other end after I removed the screw. And guess what, more metal shaving bits. And those bits of metal are non-magnetic, so not steal, but maybe part of this aluminum manifold or perhaps a stainless steel part from elsewhere in the hydraulic system? I guess all the more reason to completely take apart this manifold and blow it out? But then, how could there be bits and pieces of aluminum from this manifold, since the only moving Parts would be the spools?
Check the bores for scuffs and scratches! You gonna need pen size flash light, or even horoscope would be nice.
Is there an aluminum body gear pump in the machine somewhere? Probably not looking original to the machine?
Like I said, I would disassemble the whole thing, carefully documenting and laying parts out, clean blow of and inspect the block.
Thanks TVA, I will look at all of that. Question, what if I just removed both of the spools completely, would that not guarantee equal fluid pressure and volume going to both Drive wheel Motors?
Firs t we need to clarify which spools we are talking about, counterbalance valves or flow divider. For that you need to be 100 sure what is what, I’m not, because I’m not there to look at the components and identify them. If you will remove flow divider completely then you will have situation as working wheel differential - the wheel which has less pressure will get more flow!
And the wheel with more flow will have more torque, and therefore continue to spin if it is not getting traction, correct?
The wheel with more flow will get more speed. But it will rob the torque (pressure) from another wheel. You think someone removed flow divider?
This might be helpful to you:
thanks TVA. No I do not think anyone removed the flow divider. I was just thinking of removing it myself as an experiment to see if both of the wheels will keep spinning even if they lose traction. Currently, it is just acting like a passenger automobile with posi traction where if you get stuck in mud or sand, just one wheel is spinning while the other one stops turning. On my farm tractor for example if I drive diagonally across a ditch, and 1 rear driving wheel lifts off of the ground and continues to spin while the other one does not spin and I go nowhere, unless I engage a foot pedal that locks in the rear axle for both Wheels and the one wheel that is still contacting the ground will propell me forward out of the ditch.
Yeah! Looks like your flow divider is not working! could be spool stuck or bypassing. But I don’t like the design of this thing - it is steerable vehicle, and your flow divider should only be ingaged for short while in spinning situation otherwise you will be tearing things apart! That mis labeled component kinda looks like pressure compensated flow divider on diagram, but missing the arrows through orifices symbols! So who knows?!
The main hydraulic pump attached to the engine may not be original, since it is painted yellow and everything else is white. It is also aluminum body, except for the head portion that the large hoses attached to. The head portion is magnetic and appears to be cast iron.
The aluminum shavings can be from original pump which went bad.
So I’m still unclear, is your problem that only one side works correctly, or both sides pretty much one wheel spins while the other has nonpower?
If I jack the rear end up with both Drive wheels off of the ground, they both spin normally. But when I lower the rear end back onto the ground, both Wheels start to push the machine forward a few inches, but then the right wheel stops turning, and the left wheel continues to spin without getting traction and digs deeper into the ground, but only when the swashplate levers are in the 17 degree position. When they are in the 3 degree position, both Wheels stopped turning after they have pushed the machine forward several inches. And this is even when the main pump is producing 2500 lb of pressure. And it does the same thing even when I switch the hydraulic wheel drive motors, this is why I think the problem is in the valve manifold.
Okay, I completely disassembled the valve manifold last night and here are some pictures that I will post in this message and the next message of valves that I don't know what they are
And there are two of these ball valve looking things. Also FYI, I did not find any more of those little metal flakes in any other parts of the manifold valve body as I disassembled it.
The balls with weak springs most likely is check valves associated with counterbalance valves, there should be a shuttle valve somewhere could be ball or small spool with or without weak springs on both sides. The bigger spool looks like your flow divider and smaller ones could be the Same but these should be connected too smaller “pilot” passeges connected to the motor ports.
Swapping of the motors didn’t move the problem to the other side?
The right side of the big spool have scratches on it! I think bore has scratches even bigger ( being aluminum) and I think it is your problem.
The bigger one not even a spool in direct meaning, it’s more of a sleeve! And it’s not supposed to move aside from installing, so how it got those scratches? Does it have freedom to move inside the block when assembled?
And pictures pretty much confirm that it is a pressure compensated flow divider.
Is the 3 degrees the spec for low speed swash angle, or it’s something you measured? I think it should be somewhere half between 0 and 18 degrees.
I didn't even notice those scratches on the end of the big spool until you pointed it out, but they are so small that they are only visible with the Flash on the camera, or if I tilt the spool sideways in the direct sunlight. There are no lengthwise scratches in the cylinder of the big spool but there are what appears to be just machine sideways scratches. The big spool does not have any free play end-to-end when the cover nut is in place, but it can spin around, and I can spin it with my fingers. When I swapped the hydraulic motors 2 the opposite sides, it made no difference. The same driving Wheels acted the same way, which is why I started to look at this valve manifold block assembly. I might be able to switch the big hoses from the wheel Motors to the manifold block and see what that does, but I might have to get some longer hoses and extra 90 degree adapters. There are lots of small passages within the block approximately 1/16 of an inch in diameter. So far I have also been unable to remove the Allen screws in the side of the block even with an impactor, which you previously said you thought were for testing ports. 3 degrees is the low speed spec angle of the swash plate lever and 18 degrees was the high speed angle according to the specs, and that also looked visibly correct. I did not measure it. But I confirmed that the lever did move the swashplate when I had the hydraulic motors completely disassembled. At three degrees, both of the driving Wheels would stop turning after moving the machine several inches in either direction. And at 18 degrees, only the left wheel would stop turning, and the right wheel continue to turn and spin even though it was not getting traction. I'm wondering if I just took all of these spools and ball valves out of the valve manifold block if that would get equal volume and pressure to both Motors while disengaging the brakes at the same time?
Are the smaller spools slide freely inside big one both ways, is there any scratches or other damage inside of bigger spool?
The way the pressure compensated flow divider works is: it should proportionally cut the flow from spinning wheel. Looks like it’s working one way. So it’s either small spools do not slide one way like they should, or Fluid bypassing somewhere, or both! Maybe 3 degrees worked when motor s were fresh but now when motors are “tired” you may wanna start increasing that angle until machine will start moving. I think 3 degrees is low.
The only thing you can remove is a flow divider - but it will make the spinning situation even worse. Good idea to measure pressure right at the motors because counterbalance valves could be miss adjusted, but I doubt it! If you will take out everything the fluid will be returning to tank freely and you will not be able to get off of a parking breaks.
The smaller spools slide freely both directions inside the large sleeve spool and I did not see any scratches on the inside of that large sleeve. Actually I have the swash plates lever set to the maximum at 18 degrees on both Motors which allowed the right wheel 2 have more torque and keeps spinning digging deeper into the ground, but the left wheel just stopped after a few inches. Are the counterbalance valve's the ones with the really heavy duty springs in the pictures I uploaded on Wednesday that also had the Allen screws for adjustment? Also, just FYI, in the pictures I uploaded on Wednesday of the small spools that you told me I could lift out with needle-nose pliers, the picture looks like there is one rubber o-ring on each spool, but there are actually two o rings side by side in the groove, one a little bit larger than the other one. They do fit snugly into the cylinder bore.
Yes, counterbalance valve is the ones with heavy springs. You need to build up the pressure before they allow fluid to go through them. On the manlift everything is counterbalance, I think it’s a safety issue. I suggest you read up on them.
It’s also could be something simple like flapper inside tho hose.
Here is another consideration, in this picture of one of the connectors into the manifold from one of the large hoses going to the problem will, there was a little bit of corrosion so I wire wheeled it and was left with a little bit of pitting in the metal. I put a cap on it and submerged in water and applied air pressure as a test and it did not seem to be leaking air back through the threads. But I'm not sure what 2500 lb of hydraulic fluid pressure would do.
I did not know that these hoses could have a flapper valve inside them. I will have to take a look...
Not flapper valve, flapper means deteriorating rubber and piece peeling off the wall and blocking the flow. That’s a JIC fitting and it can only lleak to outside.
Okay thanks. I will see if I can inspect the insides of those hoses and see what they look like. And maybe even switched them if I can. So then I assume that even if that jic fitting was leaking it would not affect the wheel motor function. Here's another picture of that spool with the two little O-rings in the same groove. Any thoughts on 2 o rings vs 1 larger o ring in the same Groove?
I’ve seen it, one is O-ring the other is back up ring. You know very often disassembly and reassembly fixes things, something that was stuck gets free or something that was plugged gets cleaned. If you don’t see any damages, make sure to clean all the small passages blow everything with compressed air and reassemble, see if it will start working. If not we will start diagnosing from there.
Please read up on back up rings and O-ring extrusion. Size of the o-ring should be determined by groove size and application: dynamic or static, face seal, radial etc.
Thanks TVA! As far as blowing everything out, what do you think about dipping the entire block in a bowl of gasoline and swishing it out then blowing it out with compressed air then dipping the block back into hydraulic fluid right away? Or what about just blowing out the block with high pressure water and then blowing it with compressed air and then dipping it into the hydraulic fluid? Or this just occurred to me, plug up all but two holes on the manifold and blow it from one of the open holes so the air exits the other open hole, then close off the exit open hole and reopen another exit hole and blow it out from the original open hole, and just repeat that procedure for every connection point to the manifold?
I usually take the whole thing apart and blow everything out, and if something is not blowing out reserve to more drastic measures!
Thanks TVA!
Another, kinda silly thing to check is weather your wheels turn the same direction. You see motors are swapped, and the hoses must be swapped too to go the same direction, it happens that people when replacing hoses do not put them back on correctly. So the hose to let’s say go forward should be on the left side on the left motor then to go forward on the right motor it should be on opposite side.
Thanks TVA. The wheels are turning the same direction. I'm getting ready to blow out the manifold with compressed air, and my plan was to initially blow the compressed air in the direction of the Inlet source of the hydraulic fluid, thinking that if something was lodged , it would come out easier in the direction it came from.
Hi TVA. So I completely disassembled the valve manifold and blew it out where is compressed air and I have two questions, 1. One of the two large Inlet hoses seems to have a restriction between the inlet and the pressure compensating large divider spool cylinder, and so I am wondering if possibly it was designed that way to keep the wheel motors from going too fast in reverse? And I'm assuming that one large inlet hose is for forward and the other one is for reverse? 2. I also discovered 2 more little sleeves with rubber O-rings in the 2 smaller spool cylinders in line with the heavy duty springs however one of the little sleeves was reversed, and I am not sure which way the little sleeves are supposed to be pointing. I am guessing that it was reassembled at one time improperly. See attached picture. One end of the sleeve is beveled and the other end next to the O-rings is flat. Should the bevel end be facing the little piston? The service parts manual does not show the valve manifold parts. It just shows the entire assembly.
Are those sleeves going in to blind hole or they have a plug on the other side?
No plug on the other side, but there is a hole on the other side and the thin rod portion of the piston in the attached picture goes through the sleeve and contacts the piston on the heavy duty spring side of the little sleeve
All of the sudden got really busy!!! Look for position in which that sleeves o rings will not block the passages, also see if bore has special place for o rings will slide tighter in to. I’ll get back as soon as you can.
Wow, great advice. I didn't even know that sleeve was there until I accidentally saw the sleeves o rings in a side passage opening. So that would mean that this slave was apparently previously inserted upside down accidentally. What about my comment on the one large entry hose into the manifold appearing to be blocked? Should both entry hoses be able to carry the same volume of fluid to the pressure compensating divider spool cylinder? I assume that 1 hose is for foreword rotation and the other hose is for backwards rotation of the wheels?
As far as I remember on the diagram only one side goes through flow divider.
You are right again TVA about the diagram with only one side going through the flow divider. Great memory you have! That would explain why 1 large Inlet port does not have high volume to the flow divider. So now I am guessing that since the flow divider regulates the flow to one motor, that would increase or decrease flow to the other wheel motor, right? And it so happens that the flow divider regulates the pressure to the left side wheel, which was the one that would stop turning after a few inches of travel, while the other wheel was still spinning and digging further into the ground. So maybe the spool in the flow divider was stuck in one position because of that tiny sleeve with the O-rings that was apparently accidentally reversed in one of the smaller spools could have been the cause? At least I know now that I do not have a blocked internal passage and the valve manifold. So I guess my next step will be to reassemble everything and see how it works. Oh, and I have to check the hoses from the manifold to the motors to make sure there are no flaps or blockages.
But I'm wondering, since there are two large hose inlets to the valve manifold, if each one is 4 a different motor, how is it that the wheel motors can go from reverse to forward?
Hello TVA. Just checking to see if you saw my last two posts. As to how the hydraulic motors can reverse direction, I'm wondering if that would be controlled by the proportional valve that has the wires from the control lever and potentio meter. Which would mean that with two hoses coming from the proportional valve to the valve manifold we have been talking about, that each hose coming into the valve manifold would be for a different motor direction rotation forward or reverse, right? And since there are two large hoses going to each wheel motor, 1 hose would be for forward and the other hose would be for reverse?
Well, I reinstalled the valve manifold and now neither wheel gets enough torque to pull the machine forward or backwards. So now I am wondering if maybe the problem could be a lack of fluid pressure and volume from the proportional valve? And so I am thinking about switching the drive proportional valve with one of the other functions proportional valves as a test. Also wondering if it would be preferable instead of pulling out the proportional valves, to just switch the Outlet hoses between the drive and lift outlet connectors of the manifold. See picture
Well, I ended up switching the hoses from the drive and lift proportional valves as a test, and the Boom Lift operated at about two or 3 times faster, and the drive Wheels had even less torque. So I ruled out the Drive proportional valve as a potential cause.
So I read five or six Publications on troubleshooting hydraulics and I think I have a little better understanding of the difference between fluid pressure and fluid volume in producing wheel torque. So I tested the inline pressure to the left wheel that would stop after moving several inches and with the swashplate opened up to maximum at 17 degrees to allow maximum flow, and got a pressure reading of 1200 lb, which I think would indicate that a pretty good volume of hydraulic fluid was still going through the hydraulic motor on the left side, but not enough volume of fluid to give the wheel enough torque to continue to dig into the ground. Having set for a year now on the ground, all four wheels have sank about 6 or 8 in into the ground and apparently the wheels do not have enough torque to push the machine out of the rut. And since I live on a hillside with a 15-degree incline, I'm wondering if this machine will have enough to work to make it up the side of the Hill on a flat hard surface Road. So I am wondering how to get more torque to these wheels, go with a higher GPM volume main pump, or possibly taking apart the Hub to see if there are planetary gears and possibly changing the gear ratios so that the wheels will turn more slowly, but with more torque? There is no diagram in the parts and service manual showing planetary gears in the hubs, even though it talks about planetary gears in the manual.
Hello Ronray, I have a friend's Marklift 62 that I'm helping him with and we are having the same wheel motor/drive problems (it seems). I sent one wheel motor away to be checked out and was told that there wasn't anything wrong that would keep it from working. They replaced a bearing and the seals (it took 5 months) and it is now back in. I've swapped several of the electric proportional valves operators to the drive valve and haven't had any better luck. This machine will have very slow operation of all it's functions until 5 or more minutes of running and then boom, extend, rotate etc. all work like they should. Once in a while it will drive better than others but I know it's not right. The longer it runs the worse the drive operation gets. I'll be watching your posts for insight for our rig.
Thanks Buss! Without me pulling apart the wheel hub, which looks large enough to have planetary gears inside, do you know if these wheels have planetary gears? Also, do you know if having a higher GPM capacity main hydraulic pump would give the drive Wheels more torque? Do you know what the normal pressure should be while the drive wheels are running on flat ground?
Yes, they both have planetary gears. I have not had them apart. I have had the brake off my right side while the wheel motor was out. To get the spline to line back up when putting the brake unit back into the planet hub I had to turn the cap around to depress the pin in the middle so I could rotate the splines without rolling the whole rig. They have gear oil in them and there is a way to add oil from the outside of the hub where that unlocking cap is located. The boomlift that we have turns both wheel motors the same so our problem isn't exactly like yours but does end up refusing to move like yours does. I am going to do the test like you did where you take the vent lines off the wheel motors and see how the compares from side to side. Our boom has two 'high speed' cylinders, one on each wheel motor like your (and my) diagrams show. I had the rod coming out of the cylinder on the right side come unthreaded from the spool inside the cylinder and it couldn't pull the swash-plate back all the way to 'low'. I tripped over this by accident while I had the wheel motor out having it rebuilt. I'm not sure of the operating pressure yet as I'm still learning all these particulars like you are. I'm really thinking that I may have a problem in the pressure compensated flow divider. I will let you know as soon as I find out more. Please stay in touch. Thank you for posting your problem as I've been all over the internet and happened to find your posts here on this forum and I then joined.
For some reason, my 2 speed shift lever cylinder keeps the wheel motor swashplate in the low speed 3 degree position, so I just disconnected the cylinder and manually tilted the swash plate levers to the full 17 degrees, which allows more oil to flow through the motors and thus more torque. In the Three Degree position, the wheels would not turn at all, but in the 17 degree full position, at least the wheels would turn several inches before failing to push the machine out of the ruts. Also FYI, I completely disassembled and inspected and blew out the valve manifold block. Only one of the small spools had a small sleeve that was reversed. Prior to that, one wheel would spin while the other one locked up after rotating only a few inches. After disassembling and reassembling the valve block, now both Wheels turn for a few inches, but the one wheel does not continue to spin when the other one stops spinning. My next step is going to be to jack up all four wheels to get them out of their ruts and see if that will propel the machine forward on level ground. I'm just not sure that this thing will have enough torque to propel the machine up a 15-degree incline. To get more wheel torque, do you think that a higher GPM volume main pump would accomplish that? I also wonder if it would be possible to change the planetary wheel gear ratios?
I thought of another component, the pressure relief valve between the hydraulic pump and the proportional valve manifold, that could easily be tested that could be leaking and reducing fluid flow to the wheel Motors.
Looking at the hydraulic schematic of the proportional valve bank, it looks like each spool has it's own pressure regulator. I'm going to check this out soon as I can.
Actually I think I was wrong on the location of the pressure relief valve. It looks like it is teed into the extension function circuit on the proportional valve manifold. And the exit hose oddly goes to the emergency Electric pump and then back to the holding tank.
Bus, below is a schematic of my proportional valve Bank. Which symbol on the schematic would indicate a pressure regulator? Also below is a picture of my valve Bank proportional valves. If each one has a pressure regulator, would it be adjustable, and would that be the Allen screw on the end of each valve or whatever that thing is above each valve?
can you get me a picture of what you thought was your pressure regulator but taken from a little further away showing more hose and surrounding features?
Bus, you can zoom in on the Allen screws in the picture just below the names of the functions that are hand painted in yellow. You said you switched out the proportional valve between the drive function and other functions. Did that include switching out those parts with the Allen screws?
I meant that I did swap out the coils which are held in by the allens. They use voltage to send pilot oil to the covers just above the coils (held by allens also) and their corresponding covers on the back of the valve bank. The pilot oil pressure pushes the main spool back and forth.
I took an inline pressure reading of 1200 PSI on one of the wheel Motors where the wheel would stop turning after moving a couple of inches. And my guess is that the pressure relief valve activated and diverted the flow since the pressure relief valve is set at 1200 PSI according to the manual. So I am wondering if I would be okay too adjust the pressure up to 2400 lb on the pressure relief valve and see if that would give more torque and volume to the hydraulic wheel drive motor? And if that is okay, then my next question is where do I make the adjustment on the pressure relief valve? Attached is a diagram and picture of the pressure relief valve showing a large nut on the right side. And I am wondering if that large nut is what makes the adjustment?
I have a pressure gauge on main line pressure on the valve bank. I also have a gauge on the line where the hose to one of the wheel motors comes out of the flow divider in back. I can get 2400 lbs showing on the main gauge and only like 1400 on the gauge at the wheel motor hose. Not sure what to do next. I don't have a block like the one in your picture.
Where is this block located on your machine?
Diagram shows pressure reducing valve only on one inlet port of control valve, look on the back of your DCV for the spool end cap different than the one on the front and kinda looking like bus-junkie showed on his picture. The spool end cap on your picture looks like regular hydraulic pilot control cap. 1200psi is way too low! Should be closer to 3000 psi. The question is where do you loose your pressure?! There’s several places, I would cap outlet of counterbalance/flow divider block and check the pressure. If pressure would go up - then you loosing pressure at your motors!
Leaking high speed drive cylinder also can bleed your pressure away.
Thanks TVA. In my case wouldn't the gauge that I've got installed on the main pressure line coming into my valve bank also show low pressure if one of the motors or both are loosing/leaking oil?
TVA, what is DCV? If you look closely at my picture of the pressure relief valve block, you will see that it is bolted alongside a larger valve block with the same bolts. I think it is strange that both hoses from the boom extension proportional valve also go into this pressure relief valve (see picture) which seems to be the only pressure relief valve for the entire system. I only confirmed that this was the pressure relief valve by looking at the hydraulic schematic and hydraulic hose kit pages in my PDF service and parts manual below and also the parts list diagram in my above post. I also think it's odd that in the hose diagram below and on my machine, it appears that the pressure relief valve exit hose going back to the holding tank goes through the emergency pump? Like yourself bus, I had 2700 lb of pressure on the portional valve bank, but 1200 lb on the wheel motor gauge.
Pressure relief valve block location
DCV is Directional Control Valve. The one you have the picture of.
TVA, I think I may be confusing the DVC with the flow diverter valve in the wheel motor valve manifold. Would you be able to Circle the part you are talking about in red and post it here? You're not talking about the valve block that the pressure relief valve block is bolted together with the same bolts, are you?
The main relief ( extreme left, on the bottom) is a safety RELIEF ( meaning it’s opens at set pressure and drains to tank) is a safety feature and regulates pressure in “pressure gallery” of DVC, but each section can have its own PRESSURE REDUCING valve ( closes passage at set pressure), it’s own flow reducer, port reliefs, load check, regeneration, and etc. valves. I need to see your diagram to know what’s in it. Yours probably using fixed displacement pump and it does have relief valve ( I can see it on the picture). Ronrays diagram doesn’t show main relief probably because it’s variable displacement pressure compensated pump.
Here’s your pressure reducing valve on diagram
Can you find a tag on main control valve? Kinda looks like pretty old Parker.
Yes it will, but you can have normal pressure in Main Control Valve gallery, but your drive section can have lower pressure if the pressure reducing valve in that section is bad or miss adjusted!
Looks like the one on top is a external port relief for boom extension cylinder.
TVA, okay would the pressure reducing valve be the one in this picture with the Allen wrench inserted in this picture on the lift function? I noticed that the Allen screws on all of the functions are in different positions. So I assume this would be because they all have different reduced pressure settings?
Not 100% sure, but I think that’s where the pilot control hose supposed to connect to!
I just noticed that that diagram has a lot more discrepancies that I saw the first time! Just one extra - pilot control valves missing ( circled in red) missing solenoid symbol on each side.
TVA, my pump is a variable displacement pump 2-32 cid. Does the 2 signify two pistons? If a variable displacement pump does not have a main pressure relief valve , then the pressure gauge for the main galley should read 1200 PSI, just like the pressure gauge for the wheel motors when I engage the drive function? FYI, when I engage the other functions on the machine, like the boom lift for example, the main galley pressure gauge reads 2700 lb. Does the hydraulic hose kit diagram I posted earlier give any clues? Is the relief valve in that diagram, upper right-hand side, just for the boom extension function and not for the entire system?
The designations on hose diagram is hard to read on my end, if pressure relief has one port connected to extension cylinder and other to tank then it is extension cylinder port relief valve. If your main pressure drops to 1200 together with your drive pressure then it caused by leakage ( bypassing ) somewhere. Cap the hoses that go to high speed cylinder and see if pressure will go up. If it not that cap the hoses that go to motors and check the pressure.
This is the correct diagram for the 1986 Marklift that I'm working on for my friend. Also, the correct hose kit diagram.
That one also variable displacement pump but it does show main relief and pilot circuit relief, Ronray’s shows only pilot circuit relief. And this diagram is more correct.
TVA, I think the main relief valve on my 1981 hydraulic schematic is at the opposite end of the proportional valve bank from where it shows on Bus 1986 schematic. But I still do not see the main relief valve on either hose kit diagram? So I am wondering if the main relief valve is built in 2 the cast iron proportional valve bank manifold, instead of being a separate small aluminum valve bank manifold?
The only relief on your diagram shown is pilot circuit
Bus’s diagram shows pilot circuit (yellow) and main ( red ) Both of your pumps mostly likely has what called “pressure compensator” which is primary system pressure regulator, main relief is secondary safety device.
And both main and pilot built in to main control valve body.
Okay, so I found what may be a pressure relief valve adjusting screw and lock nut on the right end of my proportional valve Bank manifold just below the large exit hose, and also corresponding to the location on the hydraulic schematic for my my 1980 machine. And if that is what it is, it looks like the adjusting screw is almost all the way in and even with the lock nut. Your thoughts?
TVA, you also asked me to photograph the ID tags on the proportional valves. The first photo is the yellow tag on the drive function valve and looks to have a PSI rating 500 lb. The other three functions have a black tag with a PSI rating of 400 lb. Would this be the PSI required from the pilot line? I also noticed in my manual somewhere that the pilot PSI could be adjusted up to 350 lb. Mine currently hovers between 100 and 200 lb.
Those are tags from solenoids, I need the tag off of Main control valve housings. I want to try and find the pressure regulator on section illustration for you. And yes - your pilot circuit should not exceed 400 psi, that’s why you have pilot circuit relief, the one you have found.
When you say main control valve housing do you mean the proportional valve Bank pictured below? I could not find a tag or parker tag, but this Bertea name and number was cast on the end of the manifold
I can’t find anything on Bertea, even before Parker bought them out they were proprietary company producing mostly for aerospace industry.
Thanks TVA! This 1980 proportional valve Bank manifold of mine does look pretty different then the 1986 one showing in the picture posted by Bus. I will keep you posted on the results of testing with the 2 speed cylinder hoses blocked. Thanks!
Here's where I'm at with this Marklift 62. All functions except "drive" work as I feel they should. I have movement in the "low" range that is consistent now from a few minutes after cold-start until 30 minutes or so after (that's as long as I've run it). It would always fail minutes after cold-start meaning forward or reverse movement would be gone. "High" range will move the machine only on completely flat ground at a rate that is faster than "low". I can climb up what I believe is 8 degrees or so (that's all I have for a hill to try it on) in low range. I can block the drive wheels with a 2 X 4 and it will crawl over them. If I block them with a 4 X 4, it will try and try and once in a while get over them too. Is this "normal" performance for these manlifts? I'll try to post a video of the vent oil off the wheel motors also showing that the pressure is at 2100 lbs. while doing this.
Here is a link to a video showing the vent-oil off the two wheel motors of a Marklift 62. The left motor seems to exhaust/vent more but after a bit the right one will produce more. After the test the two buckets held the same amount. During this test both the gauge on the main of the proportioning valve body and the gauge here in the picture at the control block top off at 2100 psi. I had the machine trigged with a 4 X 4 block in front of each drive wheel.
Great video bus. Yes I had the same test results with the wheel motor vent lines. But I am curious that now you are getting 2100 lb to the gauge on the wheel Motors whereas before you were only getting 1400 pounds. Recall that I was getting 1,200 lb to the wheel motor gauge when wheel Motors engaged. I have not yet had the time to try this, but this was suggested by TVA: Disconnect and plug both of the hydraulic lines going to your high-speed cylinder, in your case, you have a high speed shift cylinder next to each wheel , which could indicate a possible leak of oil inside the cylinder seals. And see if that kicks up the pressure to your wheel Motors, which TVA previously suggested should be around 3,000 pounds. Also FYI, I recall seeing in the manual under troubleshooting low torque to the wheels that you should test the pressure with a 3000 pound gauge. While the manual did not actually say that the flow pressure should be at 3,000 lb, I can only assume that because they recommended a 3000 pound gauge that that should be the pressure like TVA said. And you should also unplug the wire to the 2 Speed Shift cylinder solenoid on the mini valve Bank. If this does not kick up the pressure, TVA suggested just taking a pressure reading on a wheel motor line with the function engaged but all 4 wheel motor lines plugged after the gauge. If you got three thousand pounds or significantly higher, then this would indicate no leaks within the system before the wheel Motors, and that the leakage was in the wheel Motors, if I understand the test proposed by TVA. Did you have both of your wheel Motors rebuilt?
You know Ron, with all I've done I lost track of the order in which I did things and the result of each. I may even have an intermittent problem. Right now it's better than it's been but I'm not convinced it's at it's potential. The manual and that I.D. plate on the rear of the machine both say that this unit is only going to produce 2500 psi. So unless we adjust the main pressure regulator we won't ever achieve 3000 lbs. I would think that if I could get the 2500 lbs. to show up at the wheel motors it would help even more. Maybe there is an adjustment for that. I think I had told you that I did have a problem with the cylinder on the right wheel motor and that the rod had come unthreaded from whatever piston is inside that cylinder. I never took the cylinder apart, I just put the rod back in the boot and felt around until I got it to screw back into the piston. Once it was in the 1/2" or so that was threaded on the end of the rod, I think the piston was turning because there was nothing to hold it so I couldn't get it 'real' tight. So, maybe with that rod unscrewed from the piston, oil could leak through from 'high' oil to 'low' oil and that would have lowered the pressure reading, just not sure...…….. I just got done checking and filling the planetaries, the left one was low. I had the torque-hub lock caps off to better get at the fill plug and two of the bolts didn't feel right. I put a tap in and broke it off below surface. After taking the next hub section off I'd found out that those two bolt holes had been heli-coiled in the past. My tap must have gotten snarled up on the wire coil and bound up. I burnt the tap center out with the torch, blew some pieces out with air and got hold of an end of the heli-coil and pulled the remaining thread out. I then chased the threads with the 1/4 X 20 heli-coil tap and installed two new heli-coils. She's good and back together now. The left rear tire was down to 50 lbs. and it's now up to 75 like the right side. I had taken the right wheel motor off last fall and it spent most of the winter at the hydraulic shop as parts are not readily available. Mine are Cessna motors out of Italy. The tech that took it apart had said that it could use some seals and a bearing but it shouldn't have been the cause of the lack of movement. So when they got it done I put it back in and have been playing with the many other parts of the machine to get where I am now. Even rebuilt the carburetor on this old Wisconsin V-4.
Sorry guys - crazy busy lately! You got to go with pressures listed in your specs! But most of machines I dealt with had them close to 3000psi. Like 2600,2700, 2900. One thing to know: pressure is closest related to torque, and flow to speed. So if you have low torque then first thing you check is pressure, although low can be so low that there’s not enough of it to building up the decent pressure. Case drain evaluation of the motor is only half of the deal, there’s condition exists which called “cross port leakage” and it will not show up on your case drain flow. But if you have low pressure problem - you need to find out where you loosing it. I like to start at end user and go backwards. So I start by eliminating motors by plugging the hoses and see if pressure goes up. If plugging motors didn’t give you results, then next big suspect will be center pivot, but there’s components in between. But you have to divide the system give your self direction. I would say in excavators weak drive problems caused more by center pivot ( rotary manifold) then the travel motors.
Great advice TVA! Yes, I was also thinking possibly that rotary manifold. The problem is I don't see a way to get to that manifold without being underneath the machine? I have been sidetracked with other projects lately, but my next step will be 2 plug off those hoses to the two speed shift cylinder and if that does not work, plug off the wheel motor hoses. I'm also wondering if there might be some fluid leaking through the proportional valves for the other functions such as boom lift and extension and rotation? If there was even a little leakage, would that be enough to engage that function very slowly for example? And kind of a dumb question since I haven't even tried it on the machine yet, but I'm wondering if you can engage two functions at the same time for example boom lift and extension or rotation, and if it just slows the function down when two of them operate at the same time?
Rotary manifold has top part and bottom part, it’s impossible to get to the bottom part without getting underneath of machine. But as far as i know there’s not supposed to be any other components between main control valve and rotary manifold, so you can tap in and plug right at outlet port of MAin Control Valve. If you gonna have to work on bottom part of manifold I would suggest to drain your hydraulic oil tank and plug the case drain hose on top and drive hoses. The last one I worked on would not stop leaking from those, and I got covered in hyd. Oil from head to undies while I was laying underneath of the machine.
When you using two functions simultaneously it will slow down both, I didn’t see any load check valves in the diagram - so using function with very light load on may cause the function with bigger load to slow down, stop and even “sag” or down drift.
Thanks for that great advice TVA! And sorry to hear about your getting soaked with hydraulic oil. That was a great explanation about wheel motor torque and speed as it relates to fluid volume and pressure. So let me ask you this question, when the hydraulic motor swashplate is tilted to the maximum 17-degree maximum position, that allows more flow, so my question is should the wheels be turning faster, but with less torque with this swash plate in the maximum 17 degree position, and be turning slower, but with more torque in the 3 degree nearly perpendicular closed position and allowing less fluid volume, but higher pressure, and better able for the wheels to climb over that 4 x 4 piece of wood that Bus talked about?
What would change with an adjustment to this piece?
Is there another one like that on the same block? Looks like it is counterbalance valve for drive, don’t know weather this one for forward or reverse. This valve holds you machine steady until there’s pressure on either side of the drive, so adjust one way it will take higher pressure for machine to start moving, and the other way it will take less pressure for machine to start moving, but it may start free coasting on the hills.
Yes, thank you TVA, there is one on the other side. Here is a picture.
Did you plugged the motors and checked the pressure?
Yes, I blocked the lines going that go into the motors after the block in the previous picture. Same pressure readings, 2100 psi. forward or reverse.
And what is a spec.?
I'm not sure what you are asking. A spec.? Whenever I draw the boom extension cylinder all the way closed and hold it in that position the gauge on the main valve body will reach 2400 psi or so. When I hold the drive lever in either forward or reverse, with wheel motors plumbed up or with lines plugged I only get 2100 psi.
What is manual says your drive pressure supposed to be? And that’s your gauge connected to main control valve?