M923 Transmission Fluid Reads High... Then Low.... Then High... Then Low...

[Stranger]

I thought I knew how to read the dipstick on my M923 transmission.

Engine running.

Transmission fluid temperate at ~170-180 degrees.

Transmission in neutral.

Push dipstick fully down into receptacle and pull out to observe level on the dipstick.

I can do that a dozen times and get a dozen different readings. Sometimes it is at the bottom line and sometimes it is at the top. Sometimes it shows that I have a few quarts too much. I have tried moving through R-N-1-5 with the selector before measuring. I have tried leaving it sit (running) for a few minutes and then testing. It changes in the span of ten seconds.

I swapped out the 10W oil in the transmission with Dextron III. I also swapped out the remote filter on the passengers side of the engine compartment at the same time. I took out ~4.5 gallons and that is what I put back in (minus a quart because it was reading WAY too high). Now I can't get the transfluid level on the dipstick to stabilize.

Can anyone offer a suggestion?

 

[MtnSnow]

Pull The Dipstick Out Slowly...

 

[Stranger]

I have been doing the "slow" pull consistently. I have tried slow like molasses in January, slow like "Matrix bullet-time", slow like a snake in the snow slow, etc. Am I supposed to doing it slow like... make a pot of coffee while you are pulling it out slow, or finish a quilt slow?

To be specific, with the parking brake off and depressing the brake pedal, I shift the transmission to D and wait five seconds, then to N and wait five seconds, then to R and and wait five seconds, then back to N. I pull out the dipstick and wipe off all fluid. I then gently and slow push the dipstick completely back into the orifice. I count to three-one-thousand and then veeeeerrrrrrryyyy slowly remove the dipstick. The dipstick will show fluid an inch above the full hot mark. I then clean off the dipstick, insert and remove using the exact same procedure and slow motion. Now the fluid level is only a half inch above full hot. If I wait another minute and take a reading it will be at the top full hot mark. If I wait another minute it will be down to the lower full hot mark. If I wait another couples minutes it will show up an inch below the lower full hot mark or perhaps not even show up on the dipstick. Uhhh... what?

I know there is at least 4.5 gallons of fluid in it. It hasn't disappeared or leaked out.

The only thing consistent is that the fluid level seems to go down as I let the warm transmission sit for five minutes or more in neutral (engine running) at a temperature of around ~160-170.

 

[M37M35]

I'm not too familiar with the 5 tons, but I've had the same problem on other vehicles caused by the trans vent tube being plugged. It wouldn't hurt to verify that the vent is clear.

 

[Stranger]

I'm not too familiar with the 5 tons, but I've had the same problem on other vehicles caused by the trans vent tube being plugged. It wouldn't hurt to verify that the vent is clear.

I was wondering that myself, but in reading the literature it seemed that the dipstick plug and tube actually was the vent. In the Allison tech help pages it says to make sure the dipstick vent isn't plugged.

Anyone know if there is a different vent on the transmission body?

 

[Swamp Donkey]

The transmission vents to the intake stack.

 

[Stranger]

The transmission vents to the intake stack.

I was just reading that on another thread. Not sure how to go about checking it.

Remove the spare, take the vent line off, and blow air through it?