So dealing with an older dozer that was supposed to be good to go. Reality is the driveline hydro system has issue. On this unit, the trans oil is drawn in by an engine driven gear pump, from the trans/steer clutch area, to supply pressurized oil to the trans, TC, steer clutches, and control valving. That oil is filtered via a magnetic filter screen system just before the gear pump, and is post filtered with two larger filter units. The post filters have bypass ability so if they are clogged, they will bypass oil to get the job done. So, on personal inspection, i have confirmed the magnetic filter is plugged to the hilt. Mostly silver fines but I did not totally pull the filter yet to confirm every issue. It was simply obvious the magnets were doing their job and this is the reason the pump cannot supply proper pressure/flow to the trans and clutches. The post filters did not initially show major concerns but I did not actually pull them and cut them open because I have concerns that removal will put even more metal in the outlet side. Not sure how the system is designed. It is obvious there is moisture in the system. There is still some black oil indicating this might be a condensate matter as I don't see many other water intrusion possibilities. When I drained the trans gear pump, I had black oil, gray oil, and even droplets of straight water. The symptoms previously were a loss of trans hydro pressure in the system. I think I can confirm that at least the magnetic filter to the pump caused most of that. However, those don't foul for no reason and something either died or is dying. I would like to get some experienced thoughts on how to proceed? Is it cheaper to just buy cheap oil and try to rinse the system? Will that even work? Can we rig up a crash cart to filter things and try to revive it that way? I do not have a current oil analysis. Was told it was high in "metals" but knowing what those are would help! However, without knowing the composition of materials in all of the system, it might still be a guess as to what is going on.
IMO if the amount of metal was enough to clog the magnetic strainer added to visible water in the drain stream you're in for a complete teardown and rebuild whatever is/was the root cause of the metal generation. Pulling the filter and cutting it open will not permit any more particles to pass downstream so long as you disconnect the lines to the filter housing and drain it at before you remove the element to replace it. Oil flows from the outside of the element to the inside, so the "dirty" oil will be between the OD of the element and the filter housing. An oil analysis would show huge numbers (of whatever) and be positive for water. Again another indicator to - "tear it down". A false premise IMO. The screen plugged BECAUSE something has already died. It ain't dying - it's dead. The full screen is a road sign telling you to "look upstream and you'll find the mother lode". If that screen is in the bottom of the converter housing than that's what you need to be pulling out first. Other components may follow. A replacement pump will most probably be required. You need to be more worried about fixing what's broken than worrying about system cleanout at this point. The cleanout can be looked at once you've fixed everything that's broke.
We have customers that like to play the gamble of replace the broken component change the oil and let her eat and see what happens For some reason they never are willing to pay for the repair and proper clean out but have plenty of money to replace failing components repeatedly. Go figure Pay me now or pay me later, truer words have never been spoken in regards to repairs and half measured repairs
I have no idea where the debris are originating from on the mag filter. Very hard to determine where the pickup line is. The pictures in the books all suck so its just a guess. Are the transmissions very sensitive to oil contamination? How about the torque converters? I might not mind digging into this one a bit but I think it might be stupid if it needs new clutches, transmission, TC, spools, pump, ring/pinion, etc, etc. They just aren't worth it.
I said that above. The first component upstream of the screen. Where exactly is the screen where you found the material located, in the bottom of the transmission case or the bottom of the torque converter housing.? Also how about posting a pic or two of the particles.? As stated before you have a major failure on your hands which caused the contamination. You have to find the failure and fix it before moving forward.
All I see is this is an "older dozer" and it's not worth a rebuilt trans? change the filters and the oil and see what it does. Unless it's not worth a new set of filters? Then stick it on craigslist for parts? Nige buys his trucks in sets, and assembles them himself, he has a little different standards than I do. I wonder if I could come up with an oil test for situations like this, my "white bucket flush oil analysis": drain all the oil into a clean white bucket, set aside and allow to settle, flush the component with diesel into another white bucket, allow to settle, repeat until no more debris is removed. Separate the debris with a magnet, the magnetic debris will cost $3,000/ounce to repair, the nonmagnetic will only cost $1,200/ounce to repair. Sorry for the bad joke, it would be about as useful as oil analysis on this one though.
Unlike my other equipment, the manual just sucks so I am stumbling into info bit my bit. Apparently the TC has a pump and screen filter all it's own. The book of course does not say where the pickup is but does mention the "bevel". Which as I understand, the bevel gear and clutches all run together. However, there is a picture that indicates pickup might be from the trans.... The mag screen I pulled was for the "trans/clutch pump? which is located about 2" from the suction inlet of the pump, which is mounted on the engine bell housing. The fact that the ring gear bearings were found to be bad previously would give me great concern that either something was missed by the techs (those bearings don't fail for no reason) or they did a poor job and those bearings ate themselves. I guess the only right thing to do is gut it, pull the covers (floor, trans, and clutch) and see what I can see. I agree settling the oil out in buckets I am sure with the amount of sitting, most of the fun stuff will be the "first pour" off the drain plugs. I DO know the TC and trans pump were replaced very recent. Indication was the TC vanes were heavily eroded. I am sort of wondering if that was the component that went bad, and sent its debris through the system. However, you would think an experienced CAT dealer wrench would know to look for this.
Post a photo, but my bet is the "bellhousing" that you're talking about is actually the torque converter housing, which is where I figured the screen would most likely be.
Am I missing it has there even been a mention of the make of this "dozer"? The very last sentence from the poster does seem to indicate it was a Cat so at least that is a start! A picture of the magnetic strainer as removed would be interesting if only for the shock value! If it is as bad as it sounds might be worth dumping in some of the cheapest oil after cleaning strainer and replacing filters then run a bit and drain again the inspect them to see how much more comes out. At least that you make cleaning the housings easier if someone does attempt to salvage this thing.
It’s on another thread from the same poster - a D7E.
Yes, this is a continuation of my "D7E" thread. CAT Nige, I can confirm that the pump mounted on the side of the engine is a different pump, though still not sure if it provides any oil to the TC. The TC actually has its own pump and filter that are very clear and obvious on the TC. It is a small gear pump and there is a filter unit buried down there. Where I am at here, and just a hope, the condition that parked the machine was the clutches and trans would not operate correctly. It was confirmed that oil pressure to the clutches dropped drastically when activated. However, one look at the intake mag filter for that pump would prove "why" the pump cannot provide any volume. However, as we all know, that filter should not be plugged. As I understand it, the pressurized oil simply actuates the big pistons in the clutches and locks the trans clutches together. I don't think there are any oiling port where that oil is pushed direct to critical bearings. With this hope in mind, I am hoping that the post filration did it's job, which "might" have saved a few things. For instance, those clutches are stupid simple devices, but there is a $5 Oring on the piston that if shredded, will take many hours to fix. I am hoping the oil inside the clutches is clean. hope...... I think I will first have to get all the filters out. I still am not even sure if the filter on the TC is a suction or pressure side filter...... The manual SUCKS!!! On my other CATs, the manuals are insane GOOD! They literally explain the entire theory of what everything does with very detailed hydro schematics. The schematic I have does not even show the TC pump, though it certainly shows the filter, and I know the pump is there....lol Let me dig in the books some more and see what other clues I can find.
Here’s the problem. There are no online manuals for that machine in the Cat system. Try taking some photos of the diagrams from the manuals you have and post them up so that everyone can see what you’re looking at. There will be plenty of people on here who will be able to help you interpret them. Also post the Serial Number just in case someone has other manuals that might be applicable to the tractor.
Here are a couple pics from the PDF manuals I have. Serial is 75E70x
Going by the 005371.pdf I'm seeing two separated magnetic strainers. One on the suction line to the pump #14 and one on the inlet to the oil cooler. That strainer is #4 and cooler is #3. Pump #13 is being called a scavenger and circulating pump. As the pressure tap "C" is in the line from filter #2 and that filter is connected to pump #14. That would be the pump that works the transmission and steering clutches. I would be very interested in knowing what that filter caught before it went into by-pass mode. Because if there was/is anything of any size there you can be sure every place in the system has got it's share of the crap, control valves and bearings included.
Or they come back and want us to eat the bill for subsequent failures.
I think all I can 'hope' is the filters did not bypass and the plugged up magnetic inlet screen restricted the pump thus causing the low pressure to the clutches/trans. The pump was observed to have proper pressure until certain hydraulics were activated. The #2 filter unit is pretty substantial. There are 2 filters, about 14" tall each. Not certain if one is for clutches and one for trans , or if they act in series as double filtration. A course and fine if you will. I will see if I can find parts diagrams that help paint that picture. From the pics, I am not sure how the TC gets it oil. There are pics of the inlet coming from the trans, yet a spec for that inlet relief valve as position pressure, 110-120psi. That would mean the main pump supplies it? As well, it looks like the oil goes to the TC pump, through the TC, THEN through filtration? I hope that is not the case!
Right, now the dog can see the rabbit. It's a simple system and pretty obvious how it works. There are two pumps (13) & (14), but only one of them (14) actually supplies oil to the system. The 2nd pump (13) is the converter scavenge and circulating pump. It has two fiunctions, first to circulate oil from the torque converter through the cooler and second to scavenge any oil from inside the converter housing and return it to the transmission housing. The oil inside the converter housing accumulates from internal leakage within the converter. Do you have a parts breakdown for that pump.? Is it a single-section pump or 2-section.? I think it is most likely a 2-section pump. System Operation The reservoir/tank/sump for the system is the transmission case (8). The pump (14) sucks oil from the transmission case (8) and delivers it via the filter (2) to the inlet port of the transmission control valve (9). This is also the location of pressure tap (C). At that point the flow diivides. Some goes into the transmission control valve (9), the rest heads to the steering clutch hydraulic control (5) from where it is used to supply oil to the steering clutches (1 & 11) and also to lubricate the bevel gears and the cross-shaft. The converter inlet relief valve (6) is part of the transmission control valve (9). This valve takes pump pressure and reduces to the required converter inlet pressure. It is also the location of pressure tap (D). Oil flows along the line from the inlet relief valve (6) to the torque converter (10). The pressure inside the converter is controlled by the converter outlet relief valve (7). From that valve oil flows through the magnetic screen (4) and the oil cooler (3), returning to the converter in what could be described as an endless loop. When it arrives back at the converter at the circulating pump (13) some of the oil is diverted to lubricate the transmission via the line with pressure tap (I), the rest of the flow is returned back into the converter. Simples........
I agree that pump shown in the first attachment that shows the converter housing sure looks like a two section gear pump very similar to many Cat transmission pumps:
Oops, never looked much at that attachment when I saw it was a parts breakdown, i was concentrating more on the hydraulic circuit diagram. You're right, it does look like a 2-section pump. I know logic dictates that it ought to be 2-section, it would be nice to confirm that with an internal breakdown, or an illustration of the lines that connect to it.
Yes, appears to be a 2 section pump. Question at the moment is what gets filtered and when? There is obviously a filter mounted inside the converter. I am trying to determine if that is the filter denoted in the hydro diagram or not. The converter was very recently replaced. Because of the low hours on the machine, I would not expect it to fail even the first time. It is possible the converter is dead and it would seem the scavenge pump sends 'case drain' oil right back to the trans? Where the main pump would pick it up?
From your attachment 5372 above - is the gear #13 in the illustration listed as a quantity of two.? If so that's the pair of gears for the second section of the pump. What's inside the converter appears to be a magnetic screen assembly from the parts illustration. In technical terminology that assembly is designed to remove "dogs, small children, & tree branches" - a filter it ain't.......... Is there another filter housing in the lines between the circulating pump for the converter and the cooler.? Upload the parts listing for the lines if you have it. Where exactly was the magnetic screen located that you found plugged up with particles.? Regarding "what gets filtered where", all the oil that is sucked by pump #14 is sent through the filter #2 before it goes anywhere, be that transmission, steering clutches, or converter. Everything else in the way of oil that is moving anywhere within the system after filter #2 at best goes through some sort of a screen, magnetic or otherwise. Do you have any parts manual pages that show the power train oil lines (transmission, converter, cooler, whatever).?
Yes, there are two #13's in the parts list. That sort of confuses me because you can see it has a keyway cutout, yet the parts list only calls for one woody. Never the less, It does seem to have two stages. Sure wish they would uses these stages to isolated components!!!! Unless that filter unit did miraculous things to protect its downstream friends, everyone suffered at this ballgame. OK, so, there is some indication there is another converter filter somewhere. Have not see that one yet. However, I have not found a breakdown of that filter unit. In pic 5374, the filter housing about #27 is the magnetic prefilter for the main hydro pump, and is the one that is very obviously plugged. The pump is right above it and very obvious how that is plumbed. When you look at the double filter unit in 5375, you can see the filters are the same but it is assembled differently, making me think it might be a series filter unit for the trans. What I am starting to think (CAT guys don't shoot me) is the CAT dealer did not get this properly repaired from the start as the machine predates most of the mechanics on staff. It was logged in with concerns of TC overheat. The TC was pulled and verified to be eroded so the TC and pump were replaced. As well, the bevel ring gear bearing was noted to be out, so it was changed. That is not normal. I am a bearing guy and I would want to see that bearing. Very likely to see FOD damage on that bearing which came from somewhere. Looking at that mag screen, either something died fast and furious, or it was never even touched and inspected when the TC was swapped.
I understand the difficulty of trying to interpret the Parts Manual. That’s probably because it’s not a genuine Cat Manual, the illustrations give the game away. That’s the reason for all the questions. I believe that the magnetic screen shown in the housing of the TC is actually likely to be the only mag screen between the circulating pump and the cooler. I was asking you to confirm whether or not there is another one by physically following the lines from the pump to the cooler. So the magnetic screen that you found plugged with debris is the suction screen for the main transmission pump (#12 on the Schematic), not the one in the converter housing.? Don’t get confused with the fact that it’s shown as a separate component on the schematic, it’s most likely to be built into the side of the transmission case.
It will be a day or two before I can confirm that. At some point, I will just have to move the machine to my own place, then I will have a little more freedom to comb over it. So being this is an Army spec machine, can we assume the Army put this manual together? It does not seem aftermarket and there is a LOT of info on rigging the machine, making me think so. With my other CATs, the books are very details. Very happy to see a full explanation of how the fluid moves and why.
Unless there is something somewhere that says the manual was produced by the Army I wouldn’t think so. Did the manual come with the machine or did you buy it separately.? I think what you likely have is an aftermarket manual.
TM5......... in the upper right sure looks like a military publication to me. Google seems to agree.
Lets go with an Army manual. Why they would want to write their own is beyond me..... All I can see is they adde two rigging points and green paint.
OK, the smoke is clearing. There IS a separate mag screen on the transmission pump suction line - circled in blue. The oil flowing through the suction line follows the red arrows and goes through the mag screen before arriving at the pump, then follows the green arrows to the filter and afterwards the blue arrow to the entry to the transmission control valve where, as discussed, it splits into three (transmission, steering clutches, & torque converter).
The transmission filter housing does not appear to have any form of bypass in it, unless the elements can lift up against those springs #12 & #21..? I don't know about anyone else but I've seen plugged filter elements collapse in older machines before.
Regarding your pdf 5373, that appears to be the powertrain (aka transmission) cooler and again there is a separate screen/filter housing in that system (circled). To me that layout looks like the lines to and from the converter recirculation pump. Where do the tubes #2 & #22 connect to.? I'd lay odds that #22 is the outlet from the recirc pump and that #2 will feed back into the recirc pump inlet somehow, possibly via a hose.
Yes sir! The mag filter you circled IS the one I inspected and has debris in it. I also opened one pot on the double filter unit on the trans. I did not fully remove the filter because I didn't want to cause more contamination until I knew more. However that filter did not appear to have any serious matter stuck to the outside and was not collapsed. Yes, I think the "bypass" function is pushing past the springs. Bypass is mentioned in the service book. I also agree that it looks like there is another filter housing for the converter? I will have to look for it. Seems like there is a mag filter in the converter as shown in the TC pic I posted, plus the other filter shown above? I guess it does wage 'some' hope the system has some protection. What is annoying is CAT apparently noted the low pressure issue to the clutches, THEN decided to test it for hours!!!!! WHY!!?? Because the bevel ring gear bearing was noted as being bad and replaced, I am sort of wondering if the trans pump mag filter was never even checked and was already plugged from that failure??? The condition it presented initially when in service is "TC was getting hot and would not pull". The TC and pump were replaced but I think they roasted the first one because it was deprived of oil and was slipped bad. Someone wasn't looking at gauges. They have a TC gauge for a reason. There is also a trans pump pressure gauge. It sounds like the machine returned to service VERY shortly after the TC was installed so I can only hope they did not kill that one too.
I'd suggest to pull & clean both the blue-circled mag screen assemblies (TC & transmission). It's hard to tell exactly where they are located but the transmission screen appears to be on the RH side of the machine so I guess I'd go looking on the LH side for the converter recirculation system screen. Take photos of what you remove, and clearly indicate what came from which one. Then replace the two elements in the powertrain filter housing. What Part Number of Cat element does it call for..? There may be a finer micron-rating of filter element available for "system clean-out" purposes that could help clean things up. After that strike it up and get some gauges on the transmission, steering clutch, and torque converter pressure taps to see how the numbers stack up versus specification.
With the age of this machine (mid-60's) I'm going to suggest another source of information at this point. The Antique Caterpillar Machinery Owners Club www.acmoc.org/ I think that it would be worthwhile to register on the ACMOC Forum and ask what is the equivalent S/N prefix of the "civilian" version of your D7E, because I'm sure that there will be one. That might open up a whole load of possibilities to get hold of technical and parts information for your tractor.
Good call on the cleanout filters. I guess a lot will hinge on what is found when the oil is dropped and filters come out. Obviously if there are enough chunks to fill a coffee can, I'd say a "clean out" is not in my future.....lol I was planning to get some bargain barn oil for the cleanout and let it walk around a bit (if it will) and see if it functions normally. Obviously checking pressures as well. I was hoping to pull the head off the main transmission pump but looks like that will be pretty involved as the hard lines attach on the bottom so removing the whole pump seems the only way. I'd like to know if that pump chewed up any wild animals.
By your description of the state of the magnetic screen located in front of the pump I think it would have been struggling to suck anything TBH......!! Either way it would be good to ascertain if a cleanout element is available for when you do get things back together. One thing is certain, a failure like the one you are dealing with will be nigh-on impossible to completely clean out everything. That's where the fine filter elements come in.
I'm getting to this kind of late but might have a few things to add. The basic lay out of the system is that the transmission pump pulls a suction on the bottom of the transmission housing. That oil is the same as the steering clutch oil. The suction strainer is very common to Cat dozers. All the debris that you usually find in that strainer is steering clutch and transmission clutch related. It's pretty normal for that strainer to get plugged up on an old machine that has seen little maintenance. It is not normal to see a lot of shiny stuff in it but there will be lots of steel on the magnets. Clean the strainer with some kind of solvent and you will have to blow the steel stuff off the magnets and out of the strainer mesh to clean them. Shiny chunks indicate something broken, but it could be steering clutch related, bevel gear related or transmission related. It also might be from an old failure and have nothing to do with current condition. The scavenge pump on the converter is on the converter housing underneath the drive line. The suction strainer is also there. It has been years since I've been into one of those machines, but I don't recall an access plate in the belly pan for access to either one. I believe you have to pull the pan just to see them. As I recall the scavenge pump provided lube pressure to the transmission bearings and only ran about 10 PSI. I don't recall any filters before the cooler like it shows in the diagram above. What I recall is a filter housing right next to the transmission pump. Oil out of the pump would go through the filter and then to the transmission control valve on the transmission. It went first to a safety valve spool and then to the to the direction and range valves. When you shifted into gear the pressure would drop off the torque converter and go to fill the range and direction packs in the transmission. Once those filled, the pressure would build in the torque converter. The common problem in the system was as has been observed. The strainer would plug and starve the pump which would pull air either around the strainer top cap or along the pump input shaft. The other place where air commonly enters the suction side of the pump is on those hoses at the base of the transmission. There should be a plug on top of the pump where a gauge can be plugged into. I've seen a few machines where a petcock was plumbed into that plug to vent the air that got into the pump. That is also a cause of transmission oil getting into the engine. I wouldn't recommend just gutting the system and fixing everything that could be wrong because on a machine that old, everything will be wrong in someone's eyes. If it were mine, I'd clean everything up first. Put some new filters in and run the machine noting any problems. I'd put a gauge on the pump and watch the pressures as the machine is worked. Does it go into all the gears? Does the transmission slip when running a stall test? Does the converter temperature rise up real fast and drop real slow when running the stall test? What does the transmission pump pressure do when you are running those tests? What happens when you pull a steering clutch lever? Keep in mind that this machine is a dinosaur. It will run and make money with dirty oil and lots of stuff wrong with any and all the components. You just note the quirks and run the machine with those in mind. In my philosophy, I only want to fix what I have to fix in order to keep the machine working. When it is time to make a decision to rebuild is when you estimate the cost of the parts and labor to determine if that process is cost effective over the projected live of the rebuild.
John, could the Military-spec machine be different to a “civilian” one of the same era when it comes to where those magnetic screens are located.? I’ve been doing a bit of digging offline and apparently the only equivalent to a MIL-spec 75E D7E is another 75E, which I found somewhat strange seeing as the D7E was produced in many guises in the late 60’s....
I don't know. I've never worked on a Mil Spec Caterpillar. I did see three D7F model units that were in a warehouse in Alaska that had some difference in the attachments; blade, winch and ROPS, but I never got into the build up of those machines. In the very early D8 with the oil convertors, the suction hose for the transmission pump attached directly to the rear main case and pulled oil from the right side steering clutch compartment. There was a strainer at that connection point that extended into the steering clutch compartment. I have worked on a Mil Spec Fiat Allis that was on an Air Force Base and the parts books were the same as the civilian versions.
Regarding my previous post about equivalency - here's the evidence. Thanks to Cmark because my Serial Number reference book is about 5000 miles away from me right now.
For all of you wanabe Caterpillar sexual intellects manuals for D7E 48A6883-up is as close as it gets . Good luck fastline raising the dead. Bob
Is that the same Bob that use to work on old Cats and knows them like the back of their hand?
In a word, no! I think you are thinking of Bob/Ont who passed away a couple years ago. Extremely knowledgeable, very well liked, always polite and very missed on this forum. Definitely not the same Bob.
Different Bob been working on Cats for 50 years. If you PM me your phone # I would talk about your problems. Bob
Dave, thanks for that! And DAMNIT!!! He is the second guy to leave a serious mark on me. I am in machining and learned about high precision bearings from a former SKF engineer. Then he left this world. I feel like these guys, in their last years, try to leave some of their wealth of knowledge before they leave. Bluox, I appreciate it! Certainly will do that as I like to keep the channels open. If you have been in this 50yrs, you know these 7s!
I know nout about these dozers but have often cleaned out ag tractor transmissions by filling with cheap or s/h oil ,run a little at first ,drain warm/hot (dont get burned) into a barrel ,leave over night or longer in the barrel ,tilted away from barrel pump side ,check screens , magnets (change filters pend )pump the same oil back in ,keep the pump well up from the barrel bottom and pump the same oil back in ,leaving behind the last few gallons ,topping up with other oil . Work a bit longer next time and repeat