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D6H Transmission over heating.

BazSloan

Member
Joined
Nov 23, 2020
Messages
11
Location
Sapphire Qld Australia
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.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,977
Location
G..G..G..Granville.........!! Fetch your cloth.
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.
 

BazSloan

Member
Joined
Nov 23, 2020
Messages
11
Location
Sapphire Qld Australia
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.
 

Mobiltech

Senior Member
Joined
Jan 14, 2014
Messages
1,680
Location
Sask.
Occupation
Self employed Heavy duty mechanic
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?
 

Mobiltech

Senior Member
Joined
Jan 14, 2014
Messages
1,680
Location
Sask.
Occupation
Self employed Heavy duty mechanic
Have all the suction lines been inspected for blockage. Ie screen in torque line.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,977
Location
G..G..G..Granville.........!! Fetch your cloth.
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.
 

aog_allen

Member
Joined
Nov 10, 2015
Messages
19
Location
California
Occupation
farmer/earthmover
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.
 
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