Working on a 1986 Cat D4H series II S/N 8PB01285 and having transmission and torque converter issues. History of the machine: the previous owner had the transmission rebuilt at a local Cat dealer about 500 hours ago. Not sure how much of the trans was rebuilt, I'm thinking just the clutches, seals, and reman pump, not sure about converter. New owner used the machine 6 hours and worked flawlessly. Then all of a sudden the trans would act like in would go into neutral and come to a stop, no forward or reverse. Idle engine down, put into neutral and wait a few minutes, put into gear and would travel again for a short distance. Owner removed the filter and found oil foamy and very high moisture content in fluid. Not sure how water got into the system, tho it was pressure washed and painted and I noticed a new trans fill cap. Maybe the cap was missing when pressure washing was done? That's when I got involved. We drained all the contaminated oil out, new filter and fluid, TO-4 /30 wt. Still had same issue, would travel a short distance and act like it went into neutral. Driveshaft will spin in neutral and come to a stop when put into gear. I did notice that the pump sounded like it was cavitating and possibly sucking air. Removed and disassembled pump, suction line, cleaned screen, found nothing obvious. A couple of the pump gears had some scaring, so we opted to replace gears, seals, suction hose & clamps. Reassembled and still have the same issue, but now able to travel longer distance and then torque converter overheats. Today we removed the winch and performed pressure test and is as follows - Converter inlet pressure @ 40 PSI, Speed clutch low @ 352 PSI/ High @ 378 PSI, Direction clutch low @ 302 PSI/ High @ 325 PSI, Trans pump low @ 7 PSI/ High @ 48 PSI, Converter outlet High/3rd gear @ 0 PSI (should be same as inlet pressure). When the converter gets hot and temp & fault light illuminates, gauge reads 250+. I used temp gun on converter housing and I'm getting temp readings of 260+, all trans lines, cooler lines & filter are at 150. Any thoughts? Converter, plugged cooler, trans seal leaks. converter pressure relief? Working without shop manual and on a very remote job site and not sure where to go next. Please help asap!
The convertor outlet at zero psi means no oil flow to cooler Is the oil still aerated? if so, you need to revisit the pump/suction area again. check for damaged o rings, cracked pipes and damaged flanges Have the pump seals been installed the wrong way? it is possible the outlet relief has stuck open with rust the only way to check would be to remove and inspect. It is easy to get too it is also possible that there is an internal leak in the transmission either in the brake/steering or # 3 clutch which is engaged in neutral If the pump area and convertor outlet are ok that points to a large internal leak Unfortunately it is a bit difficult to isolate. I have a plate made up that slips between the filter housing and the transmission case. what you need to do is isolate brake /steer oil from transmission oil The oil filter separates the two systems by using the priority valve. You need at least 390 PSI for the valve to open and direct oil to the transmission controls
convertor outlet relief
Hi Mark, thanks for the reply. At this point I don't believe that the oil is being aerated, I think what we were originally seeing was foaming from the high moisture content in the oil. I did perform a priority valve pressure test, but was unsure as to the correct test port. Looking at the test locations from the literature that I had was looking for a test port inline or at the filter. Then I found that the large 3/4" port on the side of the brake/steer control valve can also be used to check priority pressure. But I was still unsure if that was the correct test point, that's why I did not provide that information The pressures were 480 PSI low & 565 PSI high. It sounds like I should remove and inspect the outlet pressure valve next. Do you think there is a possibility that the oil cooler is plugged from a previous failure? I will not be able to work on the machine until the first of the week, I will then pull the pressure relief and inspect.
The cooler could be blocked, but if you have zero outlet pressure, there is no oil going to the cooler in the first place. If looking at the outlet relief valve is ok. it goes back to large internal leak in brake/steer system /transmission or bad pump/intake Remember brakes need to be satisfied first once, then transmission controls. what's left over goes to convertor
Hi Mark, I disassembled and cleaned the converter pressure relief and the only thing I found besides a bit dirty is the orifice on the poppet was plugged, spool not stuck and no rust. Reinstalled and rechecked pressure, but no change. I found another forum that a tech hooked up gauges to brake/steer control valve, speed & direction clutch, and lube pump to isolate a leak. In essence, he was cutting off a leak by applying the park brake, steer clutches, foot brake, and direction clutch individually and watching the speed and direction clutch pressure for a 20+ PSI pressure rise during each function. I tied this test but I only had enough gauges to test 4 pressures at one time. I did not see any pressure increase during this test. I also performed the pressure differential test, pressures and pressure differential was within spec. I'm now wondering if I don't have a leak in the converter. The reason why I say this is when I operate the machine until the converter overheats, the starter will leak transmission oil from the mounting flange. I know the starter needs to be resealed. but now wondering if the converter housing is getting flooded from a large converter leak?
' I found another forum that a tech hooked up gauges to brake/steer control valve, speed & direction clutch, and lube pump to isolate a leak. In essence, he was cutting off a leak by applying the park brake, steer clutches, foot brake, and direction clutch individually and watching the speed and direction clutch pressure for a 20+ PSI pressure rise during each function. I tied this test but I only had enough gauges to test 4 pressures at one time. I did not see any pressure increase during this test." I wish i was there sounds like a good problem to get into. That's why I use an isolating plate. the test gauge method is ok but a bit iffy if you don't understand what is supposed to happen. The convertor leaking internally is possible, as it does cause over heat and usually stops the engine from operating above anything from half to three quarter RPM and the engine is very slow to accelerate Also the convertor inlet pressure will be lower as well And convertors don't usually just stop instantly it is normally a loss over time and a major failure would see contamination in the screens. You need to perform a stall test but with no convertor back pressure I think the readings will be un useable Are you absolutely positive that the transmission pump and scavenge pump are OK
Yeah, Im here as well.
Yes, the pump and suction area is good. Like I said early on in the forum, I basically rebuilt both the lude pump and winch pump replacing all o-rings, seals, any gears that were marginal along with the suction hose and clamps. I even went as far as to use my bore scope to inspect the suction tube in the trans case for cracks. Also replaced the 3/8" and the 3/4" hoses the go between the trans case and the converter housing as they were in rough shape. I failed to mention while doing other test yesterday, I hooked up a low pressure gauge - 0 to 60 psi onto the converter outlet port to see if I would get any readings. What I found is at high idle in neutral I would get about 14 psi and with trans in 3rd about 5 psi, but then fall close to zero after 10/15 seconds. I'm wondering now if it wouldn't be better just to remove and tear down the trans to see if there is a O-ring that has failed and inspect the trans case for broken tubes or bad O- rings on the pick up tube housing? Or the other possibility could this problem be in the trans control valve?
i would look at the control valve next especially the convertor ratio valve. this valve dumps convertor oil to case under cold starts and during all shifts and it is a major leak point if jammed up or the orifice is plugged
Hi Mark, I removed and disassembled the control valve today and found something interesting in the converter ratio valve area. There is no spring for the spool valve??? The exploded view of the control valve that you sent me does not show this spring, but does show all others. In the rebuild instructions that I have there should be and shows one in the parts manual as well. The thing I don't understand is, how did it operate this long without it. Could the valve been stuck in one position the whole time? I'm going to order spring and O-rings needed to reinstall control valve and see if the spring solves the problem.
some have a spring some don't the spring was added later to help with valve operation
Well, it don't sound like I found the problem after all since some early versions did not have the spring. Do you think it would be beneficial to add the spring? I talked to the service manager at the Cat dealer that has worked on this machine before trying to get some history of repairs, but I guess they were not involved in the trans repairs. I did descuss what was going on and he's thinking it's a converter problem. With oil leaking out of the starter flange after operation, the oil should not reach that level and thinks that the converter is flooding the housing. Problem I have with that is you say my converter inlet pressure would be lower as well with a failure, but was within spec when tested. He also said that one test that he dose to diagnose flooding is to run the machine to the failure point, stop machine for a few minutes, then drain the converter housing to see how much oil drains out. For this size of machine you would normally drain about 1 to 1 1/2 gals, but if you drain 3 to 5 gals, then the housing is flooding and the converter would need to be rebuilt. One thing I'm curious about with a converter failure, would it aerated the oil to the point of foaming, or is it foaming due to being agitated by the converter? Looks to be a lot of work to pull the converter and want to be sure that is the problem before I go there.
This is interesting on Mark's post #13 above, and I quote: - "The ratio valve sometimes has a spring to help move the valve to the closed position. On valves without the spring, a small orifice may be located on the left end of the valve to vent oil directly to the tank. This orifice was added to improve stability on cold start-ups." Does that mean what I think it means that if the spool does not have a spring then it should have an orifice.? Does the spool installed in your tractor have an orifice.? Does the spool have a Part Number marked on it anywhere.?
Hi sir, Yes, the spool has the orifice drilled at the left end/side of spool and is not plugged. No part number on the spool or slug.
Well that answers that question... Like Mark I am of the opinion that if you are certain that there is no problem with the scavenge pump and the integrity of the torqe converter scavenge lines & fittings then the logical conclusion is that there is a major leakage inside the torque converter. Wondering out loud, could the "aerated oil" (are you still seeing that.?) be an indication that something somewhere is sucking air in through a connection that is intended to be air-tight..?u
Hi Nige, Thanks for jumping into the conversation. The more info I can get the better. I'm about 99% sure of the pump and the suction line has no leaks. As far as the other possibilities for a air leak, that I'm not sure of. When I removed the control valve, I did notice a foam lair on top of the oil in the case. This is after the machine sitting for a few days. Is there a possibility that I have a suction leak with the lines going to the filter assembly or is all the supply oil come from the one suction hose at the bottom of the case? The converter I'm unsure of. It sure seems to be pointing me in that direction from all the info I've received to date. I'm thinking I should check to see if the converter housing is being flooded. Also wondering if I should install a new converter ratio valve, slug, and the spring to know for sure that this part of the system is 100% correct and updated?
You seem to have it pretty well covered, and I agree with you about not wanting to remove a converter that maybe doesn't need removing. I don't think you have a leak in the lines to the filter because they are all under pressure when the engine is running and if there was a leak you surely ought to be seeing oil on the floor (or in the belly guards) rather than aerated oil..? I'd consider checking the amount of oil in the converter housing first, as mentioned by the Cat Service Manager. Thought - Have you ever had the scavenge line between the converter and the pump removed to make sure it is not internally restricted in some way.? If that revealed nothing the last throw of the dice would be to replace the ratio valve parts. After that it appears that you're into pulling the converter, like it or not.
When you do the flooding test make sure you don’t let it sit and idle to cool down because that allows the scavenge pump to catch up. Torque stall it , throttle back and shut engine off right away.
Thought I'd give you all an update on the machine. Here's some of the additional test and repairs I've tried. Removed trans control valve and installed the updated converter ratio valve, slug, & spring and still low to no converter outlet pressure. Tried adding shims to the converter pressure relief, no change, almost seemed worse. Removed shims that I added and actually removed 2 of the .036" shims to see if anything changed, now seems very lethargic when cold. Run machine until hot, stalled out the converter and immediately drained oil from housing, only drained out about 2 1/2 to 3 qts. so I don't think the converter is leaking. I bought a good quality digital pressure gauge and retested all pressures rather than relying 4 different gauges. Priority valve pressure (tested at steer/brake control valve) - 460 psi low rpm & 532 psi high rpm. Speed clutch 335 psi low rpm & 360 high rpm with LP plug installed. Direction clutch 286 psi low rpm & 307 psi high rpm. lube pump 10 psi low rpm & 33 psi high rpm. Converter inlet (cold oil) only 22 psi high rpm, shouldn't this pressure be around 140 psi ????. Converter outlet 5 psi high rpm in 3rd gear then drops to near zero. Looking at the hydraulic schematic that Mark posted I see the priority valve supplies the trans control valve with high pressure oil. Why would I get correct pressure for my clutches but not converter inlet? The specs for inlet pressure just says it can be up to a maximum 145 psi with cold oil but gives no minimum. I also see a resonator valve inline on the converter inlet circuit, where is this valve located and could it possibly cause a low inlet pressure situation ? I did notice that my high rpm lube pressure is below the minimum of 40 psi. I believe I tested the pump pressure when hot. Either that I need to use a lower scale gauge and retest. Nige, you asked for the serial number - 1986 Cat D4H series II S/N 8PB01285. At this point I'm totally lost as to what it could be, even Cat tech support is scratching there heads. Maybe with the additional info might give one of you the smoking gun I'm looking for. I have to thank all you guys for the input and ideas, this is really a frustrating problem.
What is your converter outlet pressure now. Your inlet pressure is low but 140 is just a max number. If you have fairly good lube pressure at least we know the oil is getting through the converter without being lost to scavenge pump. Is your torque outlet valve assembled properly.
The outlet pressure is 5 psi then falls to about zero. I've had the pressure relief off and apart, cleaned and reinstalled with new O-rings. It was a little dirty, but other than that, it looked good, there's not much to it. The first time I tested the inlet pressure, I was getting 40 psi, now it's 22. I'm not sure if that's due to inaccurate gauges or from removing the 2 shims in the relief valve. I may reinstall the shims and retest. Just a side note that Cat tech support is saying the the inlet pressure should be 145 psi ? I think they read the spec chart wrong, that is the max pressure cold. I do think that 22 psi seems very low.
The maximum converter inlet pressure as per the spec chart is designed for protection purposes. On a brand-new machine cold typically it might get above 120psi, maybe even 130 but that would be about your lot. I would expect a used machine to register significantly less than that but still above 100psi. You'll note that every other pressure on the chart is taken with the machine at normal operating temperature, the TC inlet pressure is the only one that's measured cold.
So if my inlet pressure is too low, wouldn't that effect my outlet pressure as well? Does the inlet pressure get it's oil from the priority valve through the trans control valve? What do I need to be looking at to get my inlet pressure up. I know the ratio valve controls both inlet and outlet pressures, that has been updated to the new valve with the spring. What about this resonator valve that's inline. I know it controls hydraulic pulsation, but could it cause a leak or low pressure situation? Where is this resonator valve located anyway.
No exact location specified but it is listed Ref. #21 as part of the transmission control valve. According to the SysOp it is in the line between the Ctrl Vlv and the converter, so I'd start looking somewhere around Port "A". There is a Service Magazine for it that is interesting - "A new connector (#20) is used in the end of the resonator assembly in the transmission hydraulic control group on the D4H (8PB, 9DB) Tractors. See the illustration. The new connector is hardened and will better withstand the impacts from the resonator piston than the former nonhardened connector."
start the machine in gear and check pressures. that will bypass clutch #3 in neutral and third speed which is the testing position but it gets back to low flow either pump performance or internal leak. As I said earlier I would completely bypass the brake /steer valve if just to eliminate completely from the test result
With the way the priority valve setup works it's not beyond the bounds of possibility that a leak in the steering/brake side could affect the powertrain, but it seems weird that transmission pressures are pretty well on the button but converter pressures aren't. I agree with Mark, bypass the priority valve for the steering/brake system just for a test, send all the oil to the powertrain and see what happens.
Hi guys, I finally have time to do more testing on this. Mark, is their a possibility you could send me some specs for this block off plate that you use so I can make one and also how it's used? It sounds pretty straight forward, just unbolt the filter assy and slip the plate between filter and case? Or just a thought, what about pulling the filter assy back far enough and slip a cut bolt or something in the steer clutch/brake passage to block it off? I'm not sure if there's enough room to pull the filter housing back with all the hoses attached and I believe there is a hard line involved.
this is how I made my block off plate remove the mounting bolts between filter and case slide a piece of gasket paper between the filter and case slide bolts into housing and lightly tap bolts to mark gasket paper remove gasket paper and punch out bolt holes reinstall gasket paper and tighten bolts firmly this will transfer the oil hole outline to the gasket paper remove gasket paper and cut out all holes apart from the oil feed to the brake /steering valve transfer hole pattern to 1/16 metal plate and cut leave some metal on top of plate to use as a handle install plate with gasket to the non seal side of housing it sounds like a long process but it doesn't take long and will help you eliminate one variable in this problem
So after I make the outline of the oil passages and looking at the parts listing, there is 7 O-rings that seal the filter housing to the case. Which one or ones do I leave blocked off?
Hi,The upper pipe circled is brake steer supply The lower pipe circled is return you can block off both both pipes or just supply
As i plated the filter/priority valve for a different problem. it would be easier and quicker to put a blanking plate under the brake steer valve with no oil passages open at all to isolate the brakes and steering from a leak path. the only difference would be that the internal oil pipe is still in the equation
After installing plate and my pressures to the converter come back, then the leak is in the steer/brake area and if no pressure change I would assume the leak is in the trans area.
Hi Mark, I Installed the plate and now I have no pressure to all systems. This is what I found when I removed the block off plate, the two pipes that were blocked actually appear to be under pressure as it dimpled my metal of the blocked ports. You say the upper pipe is steer/brake supply and lower is return, should I open up the lower hole assuming that it's actually power train supply? Attached is a pic of my plate.
I am not sure what is going on there. Maybe we used the wrong ports. I checked my plate and it looks about the same but it has been altered for other jobs. the only thing I can suggest is that you block off the ports at the brake/steer valve, as no oil holes are used at all. Other wise I am out of ideas at this time
i am having about same problem on d5h , i went thought steering valve and steering clutch and brakes just because of hours,almost 13000, the only thing in steering and brakes that was wore was plates between brake disk. replaced them and seals,then replaced trans pump, no help,i have owned this machine sence 3000 hrs so know what has been done,had same problem around 4000 to 4500, was clutch packs in trans, done it again around 8000 to 9000 hrs and now at almost 13000 hrs same problem, i just new i had never been in steering and brakes or tort convertor, but the presser is now telling me it is speed pack in transmission again, looks like about every 4000 to 5000 hrs does it in. well looks like more fun with wrenches. good luck, and thank yall for help,and keep safe.
Well guys, I'm sure I found the problem. I was about to start removing the trans and tear it down. I drained the trans oil and removed the trans control valve cover to disconnect the shift rods and thought I wanted to find this resonator valve before I went any further just to make sure that wasn't the problem. I removed the control valve and was looking everywhere inside the case and originally found nothing, then I looked down at the control valve cover and there it was staring me right in the face, the damn thing is attached to the backside of the cover. I wasn't looking for such a large valve, it's about 8" long and probably 1 1/8" in diameter. The plug fell out of the end along with the spool and spring. I fished around the bottom of the case with my magnet and found all 3 pieces. I need to order a few pieces and parts from Cat and I'm sure some will take a few days to get. I will post after I get it back together with hopefully good news.
Well done. Never seen one come apart before
Go any photos..?
I will post photos when I reassemble. Nige, do you have the parts listing for the resonator valve, my parts book does not show that valve.
Does this work..?
Perfect, thanks
Hi guys, problem solved! Installed new resonator base connector, spring, and plug, and just for safety sake blue lock-tite on the plug so it don't come loose again. Now my converter inlet pressure is 142 psi, converter outlet pressure is 55 psi, converter temp only went to about 170° after 30 mins of operation and worked flawlessly. I attached pics of resonator valve location and parts that I replaced - #20, 22, 24, & 25 of the above parts listing. I'm glad that I opted to replace the spring as the new one was about 1/8" longer that my original. I also posted a pic of my block off plate with the steer/brake & drivetrain supply pipe locations. I have to thank all of you for your help and input on this problem, it's been quite the learning experience. Cheers!
Test plate.
Not surprising that the old spring was tired if that valve bounces back and forth with the type of frequency I'm imagining.
Great read chaps with a good ending
Hello sirs. I have same problem with my D4H Cat is overhesring, I did overhaul werror replaced seals, rings, even the spein, and special conector,... And the temperature going on up...
Crisanta, I suggest you start a new thread -- and ALWAYS include your equipment (here, dozer) serial number with your inquiry. Kind regards from the U.S.
Hi guys, I'm back working on this dozer again. Pulled the trans earlier this week for tear down and inspection. Found the the 1st gear clutches toast and some of the piston seals have failed. Looking for the rebuild procedure for the planetary unit just to be sure it's reassembled correctly. Buying all new clutches and seals from Cat and would like to finish this up next week. Tried to get info from my local Cat dealer, but just like before they haven't been much help. Any help on this would be great. Thanks Gary
Is this what you are looking for.? If you want anything for the transmission control valve assembly it will be a separate document.
Yes, this will be great help. Thanks Nige
I do not know if that is a welded converter or not. It is recommended to replace a welded converter after a clutch failure like that. Have drilled a hole and threaded for an 1/8 inch pipe plug. Then pressure washed the heck out of them. Would never do that with a machine that parts cost so much and are so labor intensive. On a JCB I bought a converter from Perfection or Precision in Iowa. It worked great at 1/3 dealer cost.