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Stupid 5-Ton Allison Transmission Question

I picked up a M931a2 almost two years ago and it has ATF, it was an assigned truck that has 12k miles on it, it was in the 803rd but last use was Hill AFB, and it ran there as It has a lot of familiar red earth in the nooks and crannies. Ive had no tranny issues but id like to learn more about the issue as I like to run this truck, It was maintained well as it does not leak fluids and I wonder if it is original as the paint is really faded to the point of surface rust that outlines the strokes from the sprayer. the ATF in the trans is a mystery to me, Any info appreciated.
 

Csm Davis

Well-known member
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Hattiesburg, Mississippi
I picked up a M931a2 almost two years ago and it has ATF, it was an assigned truck that has 12k miles on it, it was in the 803rd but last use was Hill AFB, and it ran there as It has a lot of familiar red earth in the nooks and crannies. Ive had no tranny issues but id like to learn more about the issue as I like to run this truck, It was maintained well as it does not leak fluids and I wonder if it is original as the paint is really faded to the point of surface rust that outlines the strokes from the sprayer. the ATF in the trans is a mystery to me, Any info appreciated.
What does your data plate say?
 

Jdjohn

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New Jersey
I will say this about switching to transynd I will never go back to 15\40 it shifts much smoother I drove my m923a2 on a 2 hour trip on the highway at 58 mph and the trans never ran over 190 degrees not once I even spoke to a Allison tech and he even said your good for a 100,000 miles with transynd like I said will never go back best mod I did so far I've put over 5000 miles on it so far
 

bigsix

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huntingdon ,tn
Hey guys, I have a 1983amg 931. I was driving home and stopped to turn in. When I went to take off it wouldn't move. Like the brakes were locked. No forward gears. It wouldn't torque up like it was brakes it just bogged like it was in two gears at once. But it has reverse in R and neutral. Is this possibly air loss? My air pressure was dropped to 110 on both gauges. No wipers or horn.
 

bigsix

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huntingdon ,tn
It has been freezing and below the last couple of nights. I wondered if it could be moisture freezing up. It has been working flawlessly. But I have had no pressure for horn or wipers until I get on the road. Even with 120 in both tanks. And low air light coming​on with full pressure.
 

Suprman

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If you have moisture freezing up in your air lines all kinds of things can happen. When did you last service or replace your air dryer?
 

bigsix

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huntingdon ,tn
I have owned it three weeks. I am in process of changing everything now. The air dryer filter is next. And I can hear air venting in the intake tube . Tm says trany vents there and there is something else but I haven't found it yet.
 

simp5782

Feo, Fuerte y Formal
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I have owned it three weeks. I am in process of changing everything now. The air dryer filter is next. And I can hear air venting in the intake tube . Tm says trany vents there and there is something else but I haven't found it yet.
Text me your information and I will come up this weekend and take a look at it. More than likely its the valve at your parking brake handle. Or maybe your modulator cable snapped.
 

Jbulach

Well-known member
Steel Soldiers Supporter
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Sunman Indiana
It would seem that castrol transynd dextron 3 c-4 will meet all the requirements of Alison for general use and extreme duty I will get some and see how it drives
Will,
Did you ever do this? If so, do you have any opinion formed from the switch?
 
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My 931 has been experiencing occasional failure of the parking brake to release, so I hit the spring brake override (yellow knob on the right side). Then after a few minutes the park brake works fine. I'm thinking I should tear into it before it quits on me. My air dryer is toast and I'm looking for check valves as I've rebuilt two and the truck still loses its air quickly when I shut down, I want to replace them all. Any one know where I can get some? I've looked and have had no luck so far.
 

Jericho

Well-known member
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Location
Landaff NH
Suprman is spot on on his understanding for the addition of ABS, it is clearly stated in a number of ARMY AIR FORCE T.O.s T> D. . He nailed it almost to a tee. Iam on the fence with the trans fluid , I have historicly used ATF in tranies and Transfer cases . I have been tempted to change the oil in my M 931A@ ti ATF, but holding back, it runs fine , but does down shift as he described , when unloaded, no issues when loaded
 

Jericho

Well-known member
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Location
Landaff NH
Simp, I think based on observation that you put more heavy miles on a 5 ton than any one else here, What do you run in your trans, and what change interval do you use, and how many times have your ABS equipped brakes kicked it ? Just curious, I was going to change to ATF , but think it needs more thought. Just a side , the procedure for thoroughly blowing the trans fluid out is in the T.O. /TD /TM
 
Hey guys, I have a 1983amg 931. I was driving home and stopped to turn in. When I went to take off it wouldn't move. Like the brakes were locked. No forward gears. It wouldn't torque up like it was brakes it just bogged like it was in two gears at once. But it has reverse in R and neutral. Is this possibly air loss? My air pressure was dropped to 110 on both gauges. No wipers or horn.
I'm sitting in my 931 and yup it's the valve on the park brake handle is sticking, easy fix.
 

Jericho

Well-known member
1,180
69
48
Location
Landaff NH
IMG_0013.jpgWhen you were referring to the emergency brakes valve at the handle, here is the result of a tear down inspection , All the white is exfoliated aluminum residue, ( would be rust if it were steel. ) , no saving the valve, worked it for an hour , cleaning lubing ect, quicker to change it . Likely a result of little use and NO DRAINING THE AIR TANKS. took an hour to free up the tank drains, truck only has 4000 miles since over haul , sat in side a reserve unit in NJ working my way thru them all slowly !
 
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