M939 Transmission fluid level

[Olpa77]

Hey folks I am having some odd issues with my M925 A0. I switched over to dexron iii over the summer and changed the pan filter also. The issue I am having now is with the fluid level. I check it after every drive in neutral on level ground. Some days the fluid is over filled then others its way low. Today I went out for a 20 mile trip when I put it in neutral to check the stick there was nothing on it. I waited about a minute checked it again and it was over the full mark by about an inch. What the heck am I doing wrong? I'm pulling the stick out slow just like instructed in the TM's. Every once in a while I get some hard downshifts and once I even had a clunk when going from 3rd-2nd. I do not have any noticeable leaks. The PTO has never worked since owning the truck just a growling noise when trying to engage in neutral. I think a trip to the Allison dealer maybe in my near future.

 

[rhurey]

The PTO doesn't engage in Neutral. It engages with the engine off, or in 1-5 while not moving. (or creeping forward.).

Not sure about the rest, but interested what others have to say.

 

[1 Patriot-of-many]

Pull the stick up slowly. wipe it off reinsert, pull up slowly. Nevermind, you said you were already doing that. Shot in the dark, but have you made sure the vent hose is not plugged?

 

[Olpa77]

Pull the stick up slowly. wipe it off reinsert, pull up slowly. Nevermind, you said you were already doing that. Shot in the dark, but have you made sure the vent hose is not plugged?

Did not check the vent but I was driving in ice and snow last night. Maybe now I know why I can't get my PTO to work. lol

 

[Olpa77]

The PTO doesn't engage in Neutral. It engages with the engine off, or in 1-5 while not moving. (or creeping forward.).

Not sure about the rest, but interested what others have to say.

Okay so my PTO does seem to work but the winch still don't move. Tank is full, drum unlocked, clutch lever fully moved and all cables moving. Oh well I'll do some more research on it later. I'm more concerned with my transmission. Last night I drained the fluid so it was perfect on the stick. Checked it at least 5 times within an hour and every thing was fine. Started it this morning and checked it and it was way over filled, almost to the top of the stick. I could look down the fill tube and see the fluid. Its not spilling out though. I am puzzled as usually.

 

[Monkeyboyarmy]

I would check the vent also. I had one freeze up and push the dip stick out with about 3 gallons of oil.

 

[Swamp Donkey]

These are Allison manuals and explain the procedure better than the LO does. There's a lot of other useful information in them too.

View attachment OM1334EN.pdf

View attachment MT1357EN.pdf

 

[jwttitus]

I'm having the same issues with my trans it was low added fulid to it couple days later it was an inch over
regarding the winch, mine was not working, drum would spin by hand, pto was turning but would not operate
the winch, took motor off of winch and it would spin, took cover off of winch and it was full of water and seized,
got it cleaned up replaced oil(both sides) and works great. I did have to adjust the cables on the lever in the cab
as it was not fully opening hyd valve.

 

[frioman]

Make sure you get the transmission to operating temp. Then place it in reverse...wait a few seconds, then place it in 1-5...wait a few seconds, then back to neutral. Then slowly pull out the dipstick, wipe it thoroughly, then reinsert and pull it out again (slowly). I highly recommend you make certain your transmission is at operating temperature. I find that the levels vary quite a bit if I check the fluid at anything other than operating temperature.

 

[Floridianson]

Make sure you get the transmission to operating temp. Then place it in reverse...wait a few seconds, then place it in 1-5...wait a few seconds, then back to neutral. Then slowly pull out the dipstick, wipe it thoroughly, then reinsert and pull it out again (slowly). I highly recommend you make certain your transmission is at operating temperature. I find that the levels vary quite a bit if I check the fluid at anything other than operating temperature.

Agreed on that one. The thread on how much lube in the axles was the same. Operating temp. brought it up 1/2".

 

[MosquitoRanch]

Where is the vent? My M936 pumped about a gallon or more on the ground the other day! It came up through the dipstick tube. The truck never moved just lost fluid!

 

[MosquitoRanch]

I would check the vent also. I had one freeze up and push the dip stick out with about 3 gallons of oil.

Where is the vent? My M936 pumped about a gallon or more on the ground the other day! It came up through the dipstick tube. The truck never moved just lost fluid!

 

[simp5782]

Where is the vent? My M936 pumped about a gallon or more on the ground the other day! It came up through the dipstick tube. The truck never moved just lost fluid!

Top of the transmission. Comes off the drivers side near the rear of the torque convertor. It goes into a block on the frame rail where it connects with the transfer case vent then the line comes out of the block to the intake stack.

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