New to me D6H series 1. serial # 4RC009XX. Cant remember last 2 numbers. Torque converter running hot. After about an hour of running hard or light work the trans temp gauge will get to 250 degrees and stay. Can work it hard and them warning light will come on. I stop with park on or off and high idle It will cool back down to 250 within a few minuets but really hangs there. When I check the lower part of transmission or filter inlet or outlet with a gun the temp is 180-200 degrees. Engine water temp will get a little above 200 when working hard but cools off when not loaded heavy. I don't think brakes are dragging it freewheels so good and will not overheat if I walk it for an hour in 1st or second after the temp gauge reads 250. Soon as I purchased machine I done the following. All fluids and filters changed. Transmission details are the following, Chevron torque force 30 oil, Cat filter 1R-0741, gauge and warning sending units, All three screens. Nothing in screens or magnets to amount to anything. Torque converter had I'm guessing less than 1 gal of oil. Here are the results of a few pressure checks done with transmission gauge showing 180 degrees. Pump pressure (at filter housing cover) 370psi low idle 450psi high idle Torque converter outlet high idle 3rd gear stalled out 35 psi Torque converter inlet 50 psi high idle Transmission lubrication oil 12 psi high idle Is my pump weak or bypassing oil somewhere? not sure where to go from here. I have all the tech manuals for machine and do all my own repair work. I really need some advice where to go from here.
Had a 7H that was like this. Your TC pressures sound low. What does the manual say?
May be more than one problem. Trans temp "cools down to 250 deg within a few minutes and hangs there" doesn't sound right. The trans temp should drop like a stone, and I'm talking seconds, as soon as you select neutral. You should be able to watch the gauge failing if you are at HI in neutral until it hits about 20 deg above engine coolant temp and even then it still ought to be falling but more slowly. Cooler plugged..? Maybe need to do some in/out temps on the cooler with your gun. Also maybe an idea to find the trans temp sensor and shoot that to give you an idea if the gauge is reading the same as your gun. From memory I think there is both a sensor and a sender, one for the gauge and the other for the warning light. I'd have to look up the electrical schematic to confirm. Pump pressure not far off from memory. 450psi @ HI sounds plenty. Converter inlet pressure should be no higher than 130psi with cold oil. Even allowing for warm oil you are way low. Converter outlet pressure 50-55psi with the trans stalled in 3rd speed and all fluids at normal operating temperature. Again way low. Trans lube pressure is fine, quite high actually, which is good. Check converter outlet relief valve condition as a first step.? Did you by chance measure trans P1 & P2 pressures.? If you didn't it would be an idea. (Stalled in 3rd speed @ HI with oil at normal operating temp.)
Thanks for the replies. Shimmy1 , Yes the converter pressures are half what book is calling for. Nige, Yes I thought trans temp should drop fast in neutral . When it first starts to heat up you can get it to drop to around 235 but then run a little longer and temp will not drop and that's with water temp at 170. I didn't shoot the cooler inlet and outlet because the bottom pans were on and thought that's about only way to get close enough to check. The outside of the oil cooler checks 170 degrees checking from the top side. I should have checked the temp with a gun at the sender and sensor to check gauge. I replaced the gauge sender when i bought machine. I'm thinking the gauge and warning sender are reading correct because when gauge hits 265 the light will come on and that's what i read in the manual it should do. Yes pump pressure looks within spec and converter in and out are about half of specs. The trans lubrication oil pressure is running 12 psi high idle oil warm. Book specs call for 37.5 psi +or- 7.5 psi at high idle. So i think were way low there. Regarding the converter outlet relief valve, I didn't remove but i did pull cover off top side where spring is and worked valve back and forth with my finger and put a few more shims in just to see what would happen. I gained about 10 psi on the inlet and outlet pressures but would overheat faster after I shimmed up so I changed back. My guess i didn't have enough inlet pressure to push hot oil out after raising outlet pressure. I did not check the P1 and P2 pressures yet. The book reads should be 77 psi at low idle with load piston plug removed and another spec at low and high idle with load piston plug installed. I will have to read about the piston plug because I know nothing about it or where its at. Could the converter ratio valve be causing some of the problem? I guess I was spoiled by the old D6C that we have owned forever with zero problems. this machine is going to give me an education for sure.
Don’t worry about removing the load piston, just measure P1 & P2 stalled in 3rd speed. It will be interesting to see how close to pump pressure P1 is. Do you have any idea if the transmission has been out before.? I wonder if that’s the case and nobody bothered to replace the cooler.? Because of the priority valve setup that favours the steering & brakes over the power train there could be leakage in the steering circuit that is starving the transmission/converter side. Difficult to know where to start. I’d go for the cooling issue first but others may have a different opinion. Oh, and I think you’re going to be removing the bottom guards sooner rather than later. Just be careful if they are full of trash.
Nige, Thanks for the reply. I will check pressure on P1 and P2 in 3rd Stalled high idle when I get a chance. I have no history on the transmission. The previous owner painted the machine when he bought it few years ago so I cant tell if its been apart or not. The cooler looks to be original. When I check the temp of trans filter housing and lines in and out of filter the oil is around 200 degrees. I'm just wondering why the converter wont cool down to that temp when in neutral at high idle. Unless cooler is stopped up slowing oil flow and I have low pressure because of another problem. Or the low converter pressure not supplying converter with cool oil to cool down. No problem to remove bottom guards. Were off less than 40 hrs ago for clean up, fluid change and screen cleaning.
Check temps on in and out of cooler I have had many a cooler be plugged up have to pull it out and rod it out a piece of brazing rod works well
Dave, thanks for the reply. I plan to check cooler temps in and out. Nige, I checked more pressures today hope this helps with one of your previous replies. P1 (speed clutch) 360 to 380 psi high idle 3rd stalled. In neutral low idle 90psi P2 (Direction clutch) 300 psi high idle 3rd stalled Priority valve low idle in neutral 360 to 380psi Another thing I noticed is when shifting from forward to reverse sometimes (not often) its slow when deaccelerated and have to rev engine to engage or have to go to neutral then back to first (forward or reverse either one). Shifting between 1,2 and 3 while in forward or reverse is very fast.
Are you using a glycerine-filled gauge.? If you are, is the pressure rising and falling over a 20psi range while you are taking readings.? Usually it is steady. Is the P2 pressure also varying even though you don’t mention it.? The difference between pump pressure and P1 is quite high. Also from memory P1 is at the low end of the range and the P1/P2 difference is out of spec. That’s got me wondering if there is the possibility of a leak in the steering clutch/brake side.
Those temperatures are way over the top for normal operation. We always got worried if the temps ran over 220. I would be taking an oil sample and looking for the amount of aluminum in the results. The cooler would be my first thought about the problem. If I remember correct those cool the oil with engine coolant running through the tubes and oil running around the tubes. I've seen plenty of those coolant tubes plugged with debris from using dirty water and strangely enough, O ring material from the liner bottom seals. Your pressures are good enough to not be the problem. I have seen clutch slippage and going out of gear problems with low pressure way more that heating issues with low pressures.
Nige, No the gauge is not glycerin-filled. I think the gauge was bouncing and not going up and down. The P2 pressure was steady with no needle bounce. But could possibly have something opening up and dumping oil if P1 was actually fluctuating pressure. Should the P1 pressure at stall 3rd be close to pump pressure checked at filter in neutral high idle? Im new to working on this machine and just cant figure out why converter inlet pressure is half of spec. John, Thanks for the reply. I plan to check cooler in and out temps when i get a chance. Maybe should just pull it and replace with new to get that out of the way. When torque converter is at 250 degrees the oil at filter and in transmission is around 200 degrees. should oil at filter be less than 200? this is all checked with water temp at 170 to 180 degrees.
I recently purchased an infrared camera i feel works way better than non contact temp gun. But either way watch the cooler oil in vs out they plug up commonly pretty cheap aftermarket and they seem to last. Your scavenge pump sounds good.
rmllarue91 , Thanks for your reply. I have never used an infrared camera but I can see how it would work well. If I see cooler is not working properly my thought was to get a new aftermarket. I have used them in the past with great results. It will be a little while before I can get back to working on this machine but will post all new information.
I agree with John C. The cooler/cooling circuit should be your first port of call. Don't forget the lines & fittings just in case some large bits got into somewhere they shouldn't and and as a result partially blocked the flow. The pressure in that part of the system is not very high. Be sure to post back with photos of whatever you find. Here's the transmission/converter pressure chart for anyone interested.
Nige, I will check lines / fittings when cooler is off. I'm wondering if I should clean the converter outlet relief valve and and pull converter outlet line to make sure its clean on that end also?
It’ll only cost you a couple of O-rings so I don’t see any reason why not if it gives you peace of mind.