M35A3 Transmission Temp

[glcaines]

Check the voltage going to the gauge and make sure it is 24 VDC. It's a very simple circuit. 24 VDC goes into the gauge on one side and the wire coming out the other connector on the gauge goes directly to the sensor. Make sure the connections are good. If everything looks good, I would go ahead and replace the oil temperature sensor on the transmission, which is easy to do. I would suspect the sensor as a more likely cause than the gauge if the connections are good. You have already confirmed that the transmission is not overheating and you already have an easy to read gauge in the cab. I've attached a copy of the M35A3 wiring schematic for your use if you don't already have one.

 

[frank8003]

Thank you Frank. Are you saying bypass the temp sending unit and just run a mechanical temp gauge?

No, as always just put the little Tee and run them BOTH to see what there is to see.

 

[sue]

Resurfacing this post. I've got a similar scenario with my A3. All fluids appear clean and at the correct level (I flushed and refilled everything when I purchased it). It seemed to drive correctly, but after running for a short period of time, the transmission temp quickly hits 275+ with some simple driving (hauling zero load). I took an infared thermometor and the Allison Trans pan registers at around 165 degrees. Similar temps when I measure temp at lines headed to and from coolant reservoir and radiators/coolers. The water temp hold right around 185 degrees.

Bad gage? Issues with gears?? Anything else I should check? I just finished 2, 1 hour highway trips and seemed to drive well around 50mph (seemed to be about as fast as it wanted to go).

I R gun is cheap and useful, we have DX 3 in ours and it is unlikely that the gage and the pan temps
should be more that 20-30 apart,
“Probably “?? a bad gage or one that’s good but just
reads a little off.