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Please Help Cat D8L Transmission Overheating

Discussion in 'Dozers' started by stabber, Aug 25, 2019.

  1. nicky 68a

    nicky 68a Senior Member

    Joined:
    Apr 14, 2013
    Messages:
    554
    Location:
    england
    Those mating surfaces can often be fretted and pitted in old tractors.
    I've had same problems.
    They often cure themselves when they warm up
     
  2. stabber

    stabber Active Member

    Joined:
    May 3, 2009
    Messages:
    41
    Occupation:
    Engineer
    Location:
    Oklahoma City OK
    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!!!!!
     
    nicky 68a likes this.
  3. stabber

    stabber Active Member

    Joined:
    May 3, 2009
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    Occupation:
    Engineer
    Location:
    Oklahoma City OK
    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?
     
  4. Nige

    Nige Senior Member

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    G..G..G..Granville...........!!
    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.
     

    Attached Files:

  5. stabber

    stabber Active Member

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    Occupation:
    Engineer
    Location:
    Oklahoma City OK
    Thanks Nige - I will adjust and report back …… next weekend :)
     
  6. nicky 68a

    nicky 68a Senior Member

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    Location:
    england
    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
     
  7. Nige

    Nige Senior Member

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    Location:
    G..G..G..Granville...........!!
    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"..?