M35a3 trans troubles

[Digger09]

I've searched through some old posts stuff like that and havent had any luck finding answers to my strange problem. The trans was working fine now for some reason all forward gears and neutral make the truck creep backwards. Its like half speed of normal reverse which seems to be working ok. Any ideas of what it could be are appreciated. I dont see anything in the linkage that looks out of place. I had someone shift through all the gears and watched the linkage and it all looks correct.

 

[Jeepsinker]

Sounds like a valve body issue.

 

[AceHigh]

Are you near an Allison dealer? Maybe just tow her in for diagnosis. Are you still running motor oil instead of trans fluid? I doubt that would be it, but I never liked the idea of the motor oil. Hope it is something simple.

 

[Digger09]

Still running the motor oil.

 

[rustystud]

Sounds like you have a sticking valve in the valve body. Replace all the fluid and install new filters. Use Dexron 3 or better (don't use Dexron 5 though) in the tranny. Drain the "Torque Convertor" also.