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Please Help Cat D8L Transmission Overheating
- Thread starter stabber
- Start date
stabber
Active Member
Weekend Update:
1. The beast is back running and the following things have been fixed
a. The coolant flow sensor was changed and light no longer blinks.
b. Oil cooler changed all leaks sorted - coolant system flushed 3 times with distilled water and new premium coolant filled (Now has new water pump and regulators)
c. Both powertrain temperature sending units changed out
I worked it about 40 minutes and it did start heating up, but I didn't work it until the light would come on, but just a hair before based on the new temp. gauge. It still takes about 4 minutes at high idle to get the temp to drop to 100 deg C. Ambient temp was about 85 deg F. I did take some pressure measurements with it hot and the results were off from the previous round when it was just warmed up.
1. Off the torque converter in third gear (stall) brake on the pressure read 71 psi, should read 80 +/- 5 psi.
2. Off the transmission lube port, i read 0 at idle and 8 psi at max rpm.
3. Off the left hand transmission filter max rpm read 474 PSI.
I'm going out to the ranch to finish the pressure tests this afternoon - I have spacers for the torque converter relief valve, should I add one as per the book? Do I need to take off the entire relief valve from the TC, or can I pull just the valve body?
thanks for all the input so far!!!!!
1. The beast is back running and the following things have been fixed
a. The coolant flow sensor was changed and light no longer blinks.
b. Oil cooler changed all leaks sorted - coolant system flushed 3 times with distilled water and new premium coolant filled (Now has new water pump and regulators)
c. Both powertrain temperature sending units changed out
I worked it about 40 minutes and it did start heating up, but I didn't work it until the light would come on, but just a hair before based on the new temp. gauge. It still takes about 4 minutes at high idle to get the temp to drop to 100 deg C. Ambient temp was about 85 deg F. I did take some pressure measurements with it hot and the results were off from the previous round when it was just warmed up.
1. Off the torque converter in third gear (stall) brake on the pressure read 71 psi, should read 80 +/- 5 psi.
2. Off the transmission lube port, i read 0 at idle and 8 psi at max rpm.
3. Off the left hand transmission filter max rpm read 474 PSI.
I'm going out to the ranch to finish the pressure tests this afternoon - I have spacers for the torque converter relief valve, should I add one as per the book? Do I need to take off the entire relief valve from the TC, or can I pull just the valve body?
thanks for all the input so far!!!!!
stabber
Active Member
Weekend Update II:
So I added a a couple shims to the relief valve on the TC and the pressure was reading 78 PSI (third gear stall main brake engaged) - one thing of note, there were a couple shims already in the sleeve, as well as a washer ... Is there a max number of shims you should use? Anyway, I decided to test her out and made a couple passes and it heated up as usual ... I did notice that it stopped a bit quick after changing direction, so I went over to a hill and sure enough it wouldn't roll down it in neutral. I took off the floor plate and worked and cleaned all the linkages ... they seemed very good and free ... I was about to give up for the day and I took my little bar and tried to pry up on the main brake connector (don't know the exact term, but when you press on the main brake it engages on a plate. Well the plate went up a lot more than it ever did for me before ... I was likely too gently on it ... anyway it instantly started rolling in forward and reverse ... I pushed dirt for about half an hour and it didn't really even heat up to 100 deg C (90 deg F outside).... Could just a slight main brake friction cause such overheating? I did clean the linkages before, and it did roll pretty freely, but I can't remember if it rolled better or about the same... I guess my last couple questions would be..
1. Should I be worried about my lower lube pressures?
2. Should I be worried about the amount of shimming in the TC relief valve?
3. How can I make sure that the main break doesn't stick, can I get heavier springs?
So I added a a couple shims to the relief valve on the TC and the pressure was reading 78 PSI (third gear stall main brake engaged) - one thing of note, there were a couple shims already in the sleeve, as well as a washer ... Is there a max number of shims you should use? Anyway, I decided to test her out and made a couple passes and it heated up as usual ... I did notice that it stopped a bit quick after changing direction, so I went over to a hill and sure enough it wouldn't roll down it in neutral. I took off the floor plate and worked and cleaned all the linkages ... they seemed very good and free ... I was about to give up for the day and I took my little bar and tried to pry up on the main brake connector (don't know the exact term, but when you press on the main brake it engages on a plate. Well the plate went up a lot more than it ever did for me before ... I was likely too gently on it ... anyway it instantly started rolling in forward and reverse ... I pushed dirt for about half an hour and it didn't really even heat up to 100 deg C (90 deg F outside).... Could just a slight main brake friction cause such overheating? I did clean the linkages before, and it did roll pretty freely, but I can't remember if it rolled better or about the same... I guess my last couple questions would be..
1. Should I be worried about my lower lube pressures?
2. Should I be worried about the amount of shimming in the TC relief valve?
3. How can I make sure that the main break doesn't stick, can I get heavier springs?
Nige
Senior Member
1. Maybe.
2. No, IMHO.
3. Brake dragging will cause heating in the powertrain oil - guaranteed. Maybe the next step ought to be a disassemble, clean, lubricate, reassemble, & adjust for the steering clutch & brake control linkages..? And while you're in there check for wear in the bushes and rod ends, of which there are many.
There are 2 procedures for adjustment and it's not clear which one is relevant to your machine. I've included both. they are substantially different so it ought to be obvious which one of the two applies.
stabber
Active Member
Thanks Nige - I will adjust and report back …… next weekend 
Stabber,sounds like you are making progress.My gut feeling is still that there isn't too much wrong with it.
Could you fix a strong spring to that brake pedal to make sure it isn't dragging and give it a good few hours working?
I know it's abit red neck,but would perhaps cure it,then get it repaired properly
Could you fix a strong spring to that brake pedal to make sure it isn't dragging and give it a good few hours working?
I know it's abit red neck,but would perhaps cure it,then get it repaired properly
Nige
Senior Member
Maybe even replace the existing spring with a new one of the same Part Number. The existing one is 30+ years old by now, maybe it's getting a bit "tired"..?
Nige
Senior Member
I suggest that you should start a new thread. The D8L and D8N are totally different animals. The 8L has more in common with the 9N than it does with the 8N.(Cat changed the numbering system between the L & N series tractors, so the D8L became the D9N)
When you do post information, please start with a Serial Number and then try to describe the symptoms in as much detail as you can along with what you have done so far to troubleshoot it.
When you do post information, please start with a Serial Number and then try to describe the symptoms in as much detail as you can along with what you have done so far to troubleshoot it.
Last edited:
mikeam1
Member
We had a D8L 53Y1864. Had the same problem with the transmission overheating. We put it on a slight incline to make sure it would roll in neutral to see if the brakes were hanging up. It would roll so we assumed that wasn't the problem. We check tranny cooler and it was clean. Decided that the only thing that would make that kind of heat was the converter. Pulled the converter and everything looked fine. resealed and reinstalled the converter. finally found the problem, the brake linkage wasn't releasing all the way and the overheating was caused by the brakes dragging. You could put the dozer in neutral and push it and it would roll but that little bit of drag was all it took to cause the problem. Removed and cleaned and lubes all the linkage and that corrected the problem
cuttin edge
Senior Member
D8L, that's a big tractor for a farm. I bet she likes her fuel
RZucker
Senior Member
I have a farm customer with a 9N and a 10N.