Problem with Allison transmission. Is there any Allison experts out there?

[RDUKW]

where you able to figure out what was causing you issue im having the same problem now with my 923

I never completely pinpointed the problem. It was the converter locking in reverse. After a I did a full valve body disassembly and found nothing there I spent a few hours talking to different Allison techs. The final determination was that there was more than likely a crack in the pump area allowing pressure to lock up the trans. I never took the front of the trans apart, I just replaced it. Your truck has quite a bit smaller Alison than the LVS. First place I would check is determine from the Allison manuals where lock up is achieved in the valve body and see if your lucky and just have some contaminates .

 

[TexAndy]

It's the button on the high/low shift lever.

That button controls the solenoid that blocks/allows air to the interlock valve on the transfer case. All that does is keep the lever from slipping out of the selected position during operation.

 

[Rolling Thunder]

I dont know enough yet to confirm or deny anything that you guys have been helping me with and i thank you for all your help, but.... i just went out and checked high/low button and in was stuck it, wd40 the **** out of it popped out and worked with for a few minutes engaging and disengaging. And im still not convinced it was the problem.......but the darn thing is not giving me the same problem now. Goes into rev just fine and moves with out dying and on the pedal and same with putting in drive..... it now works. Again i have know idea if that was the issue but it is working now without the same problem with me making sure the high/low button was out and not stuck in...................????????

 

[DrillerSurplus]

I dont know enough yet to confirm or deny anything that you guys have been helping me with and i thank you for all your help, but.... i just went out and checked high/low button and in was stuck it, wd40 the **** out of it popped out and worked with for a few minutes engaging and disengaging. And im still not convinced it was the problem.......but the darn thing is not giving me the same problem now. Goes into rev just fine and moves with out dying and on the pedal and same with putting in drive..... it now works. Again i have know idea if that was the issue but it is working now without the same problem with me making sure the high/low button was out and not stuck in...................????????

This site & its members' knowledge are an incredible resource for each other!

 

[Rolling Thunder]

Completely agree 110%!!!!!! In short time i have had my 932 i have solved numerous issue and still have more to go....but you guys do give me a piece of mind that i can tackle 90% of the problems i may face with it and m35!

 

[FreightBoss]

I have an M915A2 and have been using it commercially. Recently the Allison HT740 transmission does not want to upshift out of 1st if I am on level ground it will finally shift and then it shifts through the gears fine...if I am on a grade at all it just stays in first. I have used Dexron transmission fluid...but I noticed on the thread that folks were using 15-40w. Any thoughts?

 

[akonitony]

I've never worked on that model of a unit before, but I imagine it uses a governor for it's upshifts. Probably behind an plate near the tail. I would remove and inspect it first. If no problem there, I would drop the pan and valve body and rebuild that next. I doubt it has to do with the fluid. Trans fluid is a better lubricant than engine oil, but it can also find leaks in a valve body better too.

 

[Floridianson]

That button controls the solenoid that blocks/allows air to the interlock valve on the transfer case. All that does is keep the lever from slipping out of the selected position during operation.

And it ingages the 5th gear transmission lockup to take pressure off the transfer case. As said if the button sticks it will stall the motor as soon a it is put in gear.

 

[azkcr]

I'm not sure if the switch is the same as a M939, but I had a problem with mine as soon as I would put it in gear it would kill the engine. Turns out the lock out switch was pushed in and had to pull it out to get it to work properly. I took it apart cleaned it out now it works great.

This is 6 years later, and this forum still saved my butt. Once again.

Our 5ton/brush fire truck was dead in ththe water with this same issue.

Do yall know what the button on the end of the 4wd lever is technically called?

 

[simp5782]

This is 6 years later, and this forum still saved my butt. Once again.

Our 5ton/brush fire truck was dead in ththe water with this same issue.

Do yall know what the button on the end of the 4wd lever is technically called?

It is called a Transfer case lever switch.

Member swampdonkey has them for sale

https://www.steelsoldiers.com/showthread.php?163158-NOS-M939-Transfer-Case-Shifter-Handle

 

[Those Military Guys]

most of the time the buttons are broken or wires cut no problem if other then you cant move the high low level unless you dump air or disable the piston on the top of the transfer case