Got a d6h that gets hot when running in 1st. It takes a good 1-1.5 hours to get it hot. Once it gets hot I can put it in 2nd and push for a few minutes and it cools back off. I was running it the other day and it was in the 90's and the water temp was running warm also, around 210-220, and then I couldn't get the transmission to cool off either. But usually the water temp runs cooler. Once the dozer gets all good and warm and the transmission temp gets on the hotter side, it is not as smooth shifting into forward and reverse while in 1st, 2nd is just fine. The few pressure test I have done are a little on the lower side. Pump pressure is around 410 psi Priority valve is at 400 psi which I think is ok. Converter inlet pressure is at 75 psi. Transmission lube pressure is ok. Any ideas or suggestions?
serial number please, there are too many differences to besure. Is it a diff steer model has any recent work been done did it happen over time or quickly from what you are saying it suggests you are losing oil flow through the transmission cooler but only in first speed it is possible that number 5 speed clutch seals could be leaking or some where else I would perform a stall test in each speed range and a full pressure check at the same time Mark
X2 on the stall test for sure.
It is a diff steer. Haven't had the dozer very long do not sure if anything has recently been done. Serial is a 3zf00755. What pressures should I particularly watch when I stall it?
Torque outlet pressure and lube pressure are good indicators of cooler oil flow.
I notice that nobody has mentioned the cooling system so far. Is the radiator spotless, all guards/ducting in place, fan belts correctly tensioned, and after that when was the last time you dropped the belly guards to clean out all the accumulated mud and debris..?
Power washed the radiator the other day before I ran it. Tightened the fan belts at the same time. Belly guards were off in the past 10-20 hours. All the shields seem to be in there. I will check the pressures in the next few days when I move it.
I would look at the pulleys as well for wear.
Finally got the dozer moved and did some testing. I can't get the transmission lube pressure to read much pressure at full throttle. The torque outlet pressure reads about 50 psi in 2nd and 3rd, stalled and forward/reverse. 1st as soon as you go forward or reverse it drops to 0, put it back into neutral 50 psi again. Could this be a sign one of the clutch's is out or do you think it's a torque converter issue?
Try pulling up the cab floor plate and watch the shaft between the converter and the transmission. It will spin in neutral but should stop dead immediately you engage any gear. It may just rotate a hair if you shift from one gear to another. I'd be very interested if it does actually stop when you shift from neutral to 1st gear. Also it might pay to remove the power train oil suction strainer and see what it contains. The spec for lubrication pressure is 37.5+/-7.5psi at High Idle. Could it be that the gauge you're using may not be accurate at that pressure..? Also can you post a Serial Number. Lots of variations on D6H are out there. See Mark's post #2 above and provide the answers to some/all of his questions will also help others to help you.
Serial is 3zf00755 It could be that the gauge is not that accurate that low. I will try and different one when I watch that shaft. It's a newer to us dozer. I don't think any major with has been done recently besides us just changing all fluids, but I'm thinking that's why this dozer was being sold. It's a dif. Steer. Fan pulleys don't seem worn.
Tested that lube pressure again today. At high idle it's at 20 psi, supposed to be that 37.5. the drive shaft only stops moving when I stall the dozer. Neutral it's spinning fast and when input it in any of the gears it doesn't slow down,just when it's stalled it stops. Where is the transmission pump suction screen at?
the spec is 37.5+/-7.5, so you're allowed down to 30psi and still be within spec. A lot of gauges are pretty inaccurate at that sort of pressure. I think the recommendation is to use a 50psi gauge for that particular test. Did you happen to test it a Low Idle, I think the spec is like 1-2psi minimum, your gauge might not even flicker at that pressure. Let me get this right about the transmission input shaft. With the machine stopped, engine at low idle, trans in neutral, shaft spins. Engage any gear with engine still at low idle, shaft stops dead..? Correct..? As you shift the gears the shaft may just turn a few degrees depending on how quick you shift from one gear to the next, but should then stop again. This test is all done at Low Idle, no engine speed more than that is required. Transmission suction screen is at the bottom of the transmission behind the small cover fixed by the bolts ref #6 in the photo below. You will need to drain the transmission oil before removing the cover.
The shaft only stops if I stall the dozer. At low idle, going from neutral into first, the shaft does not slow down. Seems the same for the other gears also. The lube pressure may be fine then. At low idle it should have that 1-2 psi. I tested it all on a 100 psi gauge.
When you describe what happens "going from neutral into first" regarding the input shaft, does it do the same for both forward and reverse..?
It's the same forward and reverse, the only time it seemed the speed of the shaft would change is when I was applying the brake and then it would stop once the dozer stopped moving.
You are doing the test with the brakes applied aren't you .....??
No, maybe that's why I'm confused. I will do that tonight and let you know. Thanks
Sorry. I never mentioned it, kinda assuming that you knew to do the test with the brakes on. No worries, do the test with the conditions above plus stand on the brakes while you're doing it and let's see where that takes you.
You need to check the magnetic strainer it is located on the right side as you sit in the seat have to remove floor board or belly pan
I did the test like you said. When going into 1st gear it is very slow to stop, if it even does stop. Couple times it just kept spinning. It seems the same for forward and reverse in 1st gear.. 2nd and 3rd stop as soon as you put it into gear, forward and reverse. I'll check the strainer
You might want to pull filter first , the parts you are looking for will go thru the screen and into the filter and you don't have to drain the oil. Bob
Sounds like the 1st speed clutch has gone South. To confirm that have a good look at the oil. Does it smell burned and/or is it very dark and cloudy (as opposed to clear & bright)..? The reason I suggested to check the strainer is because that's where all the large particles from the friction discs after a failure would most likely end up. It sounds like your transmission is going to have to come out any way so draining the oil to pull the strainer isn't going to affect things one way or another because the oil would be dumped anyway. Here are the instructions to remove the transmission because I think you're going to need them.
Fluid is very dark. Will keep you updated on what we find out
Drain the oil, pull the screen I mentioned in post #13 on Page 1, and let us know how much black burnt pieces of friction material you find in it. it should be pretty full.....
Not having any direct experience with D6H dozers and minimal with dozers in general I stayed back from this thread as there were others more knowledgeable helping. My first question on this one would have been about the subject line. Says "Gets hot in 1st" does that mean it can be run in 2nd and it stays cool, or at least "normal" operating temps? If that is/was the case it would scare me or at least my wallet and spare time! All the checks and test above do point to a bad situation. I would suggest if it's not too late that before draining the oil to pull the filter that machine be parked some place clean to work on when it comes time to remove transmission. Hate to say it but that sure seems like the next step in this process.
Good point Ken, before immobilizing the machine get it somewhere where it can be worked on safely and conveniently, and consider access to the back end for a "suitable lifting device", as Cat Service Manuals love to tell you, to snatch the transmission and bevel gear assembly out - 2000 pounds give or take. If the tractor only has a drawbar rather than a ripper that will make the removal process a lot simpler. It might be nothing more than a "soft" failure of the 1st speed clutch. As a bare minimum it would likely need new friction discs & plates in the 1st speed clutch, maybe also discs/plates in the forward direction clutch while you're in there (TBH I would, whatever they looked like), a set of new piston seals in all five clutches, and a gasket/seal kit.
As you said in your pressure testing torque outlet pressure drops to zero in 1st gear. That tells you you are losing oil somewhere when in first gear. Probably clutch #5 piston seals. You also said the shaft barely stops spinning in first that means number 5 is slipping. Make sure your shift cables are moving the speed spool properly. You could do more pressure tests to confirm but pretty sure it's got to come apart. If it has no winch it's a very easy removal.
All check the screen and the filter hopefully later today. Going to make some room and get it in the shop. We have not even put the hitch on the back of the dozer so the dozer is bare in the back. Shouldn't be too bad. I'll take some pictures of what I find
Post a photo of what material you find in the screen. There will be a number of us interested in seeing what material comes out of it. The procedure I posted above was only for removal of the transmission & bevel gears as a group, then reinstalling them after repair. It doesn't include splitting the bevel gear group from the transmission or disassembly & reassembly of the transmission. I don't know if you have a Service Manual for the tractor so if you need those additional procedures just ask.
Here is a few pics. Hoping to pull the transmission all the way out tomorrow.
The first photo confirms a burned up clutch. The good thing is that there doesn't appear to bre any metal in it which kinda confirms my theory of a "soft" (burned clutch disc) failure rather than a "hard" (metal parts) failure. The second one suggests to me that you might consider replacing the power train cooler while you're repairing the transmission. The "milkiness" of that oil drain stream has got me thinking that there could be some coolant mixed with that oil, although the photo might be a bit deceiving. Were you topping off any coolant regularly in the radiator before this problem started..?
No. Never had to out anything in the radiator. When the fluid was draining out of the dozer it had a lighter color. Once it sat in the drain tub it looked like used engine oil.
That transmission is going to need some serious cleaning on the inside! I'd be looking at a total disassembly and some quality time with parts cleaner. I think your 1st gear disks are going to look like these: Well maybe not exactly as those are the clutches out of my Sportster I removed yesterday, so they are a bit smaller but the same idea!
If you're not topping up coolant on a regular basis then maybe my perception of the oil in the photo being possibly contaminated with coolant is not correct. The transmission will get cleaned out when it's disassembled for repair, it's the rest of the power train oil system I'd be worried about. Obviously the transmission filter will get changed and the filter housing cleaned but what about everything that's lying in the oil lines..? I'd also try draining the converter housing just to get whatever of that horrible old oil is still lying in there. As a flushing procedure for the power train oil system I'd suggest filling the transmission initially with SAE10W TO-4, then just run the engine to bring everything up to temperature shifting in and out of every gear but not putting the transmission into full stall, then immediately drain the oil. Take a look how clean it is and consider repeating the process if necessary. When the oil that's drained out finally comes out clear and bright fill with SAE30 TO-4 and let 'er rip.