6 speed Allison won't move under ~100*F fluid

[Yellow Jacket]

A friend dropped his truck off a couple days ago, 06 LBZ, if you try reverse or forward it will start to move and limp out of gear and throw a shift range inhibited and codes p0700, p0751, p0761, p0762, p0877... If you let it run long enough to get over 100-110*F on the trans temp it will run and shift every gear just fine..

My first thought is fluid level low?!? Any suggestions or similar situations?? I'm gonna look at it after work today, just wanted ideas for things to check out.

Thanks in advance for any help or suggestions.

 

[03_DMAX]

Pull the main harness plug and see if its leaking oil. Had one do something similar before.

 

[jc1843]

Possible the inside filter is restricted. After the fluid is warm it flows better.

 

[Mike L.]

Possible the inside filter is restricted. After the fluid is warm it flows better.

That's where I would start.

 

[Yellow Jacket]

I forgot about this, when I received the truck, and 10*F outside temps the trans fluid level was not even on the dipstick at cold idle...

I dropped the pan and put both filters on trans, got fluid level corrected, and no codes anymore.

 

[melms23]

Glad this got bumped up. I'll have to check it out, I didn't think it was such a simple fix.