hi please help. I have an old d6h that has transmission temp overheating, to the stage that smoke comes out the breather. this has been an ongoing problem for a while. the transmission was recently opened and new discs and seals put in. Torque converter was also done with new seals and bearings. A new trans pump was also fitted. oil cooler is clean. engine oil cleaner is clean. suction filters are clean. radiator is clean and belts are tight. brakes and clutches seem fine and pressures are good. All pressure are within spec except for the trans lube pressure, it is low at 20psi. Is there any way to increase this pressure as I understand this is an indication of cooler oil flow ? I have read about a lube pressure oil orifice but I don't know where to find this ?? thank you
a few more things, propshaft stops in gear at high revs with brakes on so that means no slipping. it takes about 2 hours to overheat.
Please post a Serial Number. I'm assuming that the reason you pulled the transmission was clutch pack wear.? You say the "cooler is clean". If you had failed/burned clutches I can pretty well bet money that the cooler isn't anywhere as clean internally as you think. SOP when doing a transmission overhaul like you have done is to replace both pump and cooler. Have you checked the powertrain oil in/out temps at the cooler connections with an infra-red temp gun.? If the 20psi trans lube pressure is at High Idle, what is it at Low Idle.? What's the converter outlet pressure with all systems at normal operating temperature, the transmission stalled against the brakes in 3rd gear, and the engine at High Idle RPM (or as near to HI as it will go)..?
converter outlet is 60psi. lube pressure at low idle is 0. after letting the machine idle for 10min the temp comes down. im fitting a new cooler this weekend and will update on any changes. what is the maximum temp the transmission can run at all day ?
The temp will go up and down a bit as the machine is either pushing or tracking, but as an average 95C would be about right, and don’t let it go over 115C as a peak. I don’t know if you bought a cooler yet but I think you can get Reman which will be significantly cheaper than new. A Serial Number would be required to identify the correct Part Number.
Before you go fitting a new cooler do a test of cooler efficiency. Get the machine hot (till the converter high temp alarm goes off) then select neutral & apply the park brake. Keep the engine at High Idle speed. How fast does the converter outlet temp come down..? If the cooler is working right it should drop like a stone, because as soon as you take away the heat source the cooler should suck out whtever is in the system until it comes close to engine coolant temperature.
Our 6h did the same we changed tourqe convert as it got very hot but that was not the problem after 2 years of screwing around with it we pulled off final drives and had a break dragging. We also had to take out the brake control under seat and it was full of sand like ****. After cleaning that and putting in new brakes our heat issue totally disappeared.
The brake settings are very important on those machines!
Let me just add something for clarification. Before doing this test the engine has to be warmed up to normal operating temperature, say somewhere around 80C. Coolant thermostats fully opened in other words. If you perform the test with the engine at a lower temperature it can potentially skew the results because of the massive temperature difference between the coolant temp and the temp of the oil coming out of the converter.
Seals and bearings in the torque converter is not a satisfactory overhaul or rebuild without checking the clearances between the impeller, turbine and stator. More than twice I've had to go back and redo someone else's work because they didn't understand where heat comes from after a rebuild.
I’ve got a very similar problem. New pump, clean radiator and cooler. Pump pressure fine, priority valve fine, tranny inlet low, tranny outlet ok. Lube pressure low. When you start the machine after it’s been sitting tranny inlet pressure drops from 100 to 80 over about 1-2 mins. Lube pressure also drops from 20-14 over the same time. That’s full throttle. Machine drives fine. No slipping clutches anywhere. Cleaned all strainers. any help appreciated. Serial no 2kd00780. Clutch steer.
I suggest that you could post some pressure readings rather than "Pump pressure fine". It helps. What are transmission P1 & P2 pressures with the oil warm and the converter stalled in 3rd speed..? What's the history of the guts of the transmission & converter.? Any recent repairs/overhauls.? You say "Clean radiator & cooler". Has the cooler been off and at least inspected internally recently.? Leakage in steering system starving transmission of oil..?
We had same issue would work 100% for about an hour then oil would start getting very hot. We changed everything! Ended up being a brake dragging! All systems checked out good when outfit sat there running so no one could figure it out. When you started to use it it would heat ,and when it heated it took out the torque converter , our cooler was also plugged with material which they always said was transmission disk material but was not ! It was brake material! Take brakes apart! Do both sides !
Thanks for replies everyone Pump/priority pressure at idle 420psi p1 low idle 320 P1 high idle 350 P2 low idle 260 P2 high idle 300 Converter outlet 60 Converter inlet 80 Lube pressure 14 P1 consistent for each gear. Haven’t got any history on machine. Looks like the tranny has been out though. Has about 9000hrs on machine. Had oil cooler out and cleaned. I don’t think it’s a brake dragging I agree it’s losing oil and not enough going through cooler. Trouble is where???
Were P1/P2 HI pressures measured at 3rd speed stall with engine & powertrain up to normal operating temperature.? I can't think I've ever heard of a cooler being successfully cleaned internally, despite "radiator specialists" swearing that they can get them as good as new inside. I'm not necessarily convinced that it's your problem though. With the steering having priority in that system my suspicion would fall on an internal leak in the steering that increases with temperature siphoning off the oil flow to the transmission as a possible cause.
If it was the cooler there should be no reason for TC inlet pressure to be low but I was thinking. Any idea how to check leakage in steering circuit.
You're right about converter inlet bieng low, although it should be pointed out that the 115psi spec is generally a maximum with cold oil that should not be exceeded. That's why it's non-adjustable. 80psi is on the low side and could possibly indicate that something is leaking somewhere. Something in the back of my mind about a blanking plate to go behind the priority valve to block the outlet passage from the PV to the brakes, but that may have been on a different model. On the face of it there is no reason why a similar idea ought not to work in your case though.
Nice, I’ve checked the bracket and clutch lube pressure at the final drive flange. I got between 11-13psi both sides. No difference if the brakes applied. Do you think I should blank off the oil to brake circuit
Some more news. Took SCAB off and made a plate up to go over oil galleries. TC inlet pressure 85psi Lube pressure. 10psi
Well in that case it appaears that the brakes are not the root of the problem. Have to look from the priority valve in the other direction. Logically that indicates it must be on the transmission side. Reading back through the thread I originally thought the transmission had been out on your machine, but then I realized it was the OP whose transmission had been overhauled, not yours. Have you been inside the transmission control valve yet..? Could you possibly try some compressed air on the transmission clutches to see if there are any obvious signs of leakage.? Forward direction of 1st speed clutches would be the obvious prime suspects.
Yes I don’t know history of machine but looks like tranny has been out. No slippage in any gears. P1 is within spec ( will have to check pressure is in workshop and I’m in bed) seems about the same in all gears. Have had valve out and cleaned/refitted. I have another D6 and am hoping it will be home soon and I’ll swap the tranny valves over. Seems strange that when I first start the pressure is up over 100 and it drops to 80 over about a minute or so. Will time it next time I test. Maybe I should bypass the cooler too and see what I get.
I think at this stage it's a case of eliminating things one at a time until you get to the root cause. The drop of pressure as it warms up is telling though. Something is holding (after a fashion) when it's cold but not once it warms up. I think it has to be a seal somewhere, but I've been wrong before.
Ok no I have now bypassed the oil cooler and still have SCAB valve blanked off. Started it up torque converter belt went to about 110 and slowly dropped back to 90. Lubrication pressure started at 25 and slowly dropped back to 15 at full throttle.
Approximately how long does it take for that to happen after startup.? I assume it's TO-4 but what grade of oil is in the power train hydraulic system.?
Is the trans oil level dropping when the pressure drops off? Have you checked if the torque housing is flooding due to leakage or bad scavenge pump operation? Is the oil foaming or aerated?
New tranny pump fitted. No aerated oil. Not sure of oil.
Have all the suction lines been inspected for blockage. Ie screen in torque line.
I have had one of the metal lines crack that is on the inside of the dozer frame you have to pull trans to get to them
Thinking about it a hairline crack in a line might just produce the symptoms the OP is describing. A small leak with cold oil that gets worse as the oil warms and thins. Baz, if you're not sure of the oil I would suggest to drain whatever's in there now and try filling it with SAE50 TO-4 for your climate conditions in the interior of QLD.
We had a similar issue.. You might try the trans oil filter. The H can't handle the ultra high efficiency filter that parts recommends, go back to the original filter designed for the machine.
The "standard" element is a 1R-0741. From the comment above if you have a High Efficiency 132-8876 P/N installed then it might be worth going back to the original part number.
Ok hope Nige can give some advice. Same tractor similar issue. Problem I have now is I have to nearly have it at full rwvs to select a gear. I’m thinking pump but what’s your thoughts. Pump pressure Cold full revs 480psi Idle. 380psi After a few hours when oil is hot Full Revs 400psi Idle. 80psi Haven’t done any other pressure tests.
Questions: Does the oil smell burned.? Is it clear & bright or dark & cloudy in appearance.? Have you changed the oil recently and if you have did you remove the suction screen to inspect for debris.?
Haven’t done the screen and the oil does look dark. Doesn’t smell burnt but
In that case the first thing I would suggest is drain the oil - into a clean container if you fancy the idea of re-using it. Then pull the suction screen and post photos of what you find in it. Also indicate how many hours the machine has run since the last time the screen was pulled.