01 8.1L Ally "Wont move"

[GM Guy]

Hey all,

We have been offered a 01 GMC K2500HD 8.1L Allison Reg. Cab 8ft flatbed truck.

Pretty straight unit, and he is only asking 1500.

The previous owner sank 4 grand into the transmission getting it rebuilt.

Current owner ran it for a while, and then one day he got in it and it would not move. He did not remember if the circle around the indicator flashed or not.

He did say that occasionally the speedometer would die and come back, abs, check engine light, etc. Basically all that was working reliably was the tach, fuel, oil pressure, coolant, and volt meter.

It has been off road alot, was a cowboy bale bed truck first, then the trans rebuild, then the current owner had a flatbed on it and used it around the farm.


SO, I wanted to ask you guys what the worst case scenario on this truck would be? could there have been a rebuilder or installer error the last time around, and there could be major issues, or is it sounding like a speed sensor and a NSBU would be all that it would need to fix it?

Any input appreciated,
Thanks!

 

[GM Guy]

also, what could a guy expect to dump in a "rebuilt exchange" or hiring an allison dealer to OH the current?

Thanks!

 

[THEFERMANATOR]

Get a code reader on it first. If it won't go into gear, there should be codes present in the TCM. Without code info, its like throwing darts trying to guess. Theres a good chance a torrington got installed upside down and done serious $$$$ damage. Or it could be a NSBU switch failed open, to a stuck on torque converter solenoid and the TCM protecting the trans. You can normally pick up used 5 speeds for $1000-1500 that were running takeouts, a GM reman is close to the cost of a built trans last I checked. Its not that expensive to rebuild one really unless theres hard part damage, then it's $$$$. You can also go underneath it and unplug the round trans plug from the trans case on the rear passenger side and see if you have reverse and 3rd. If you do then theres hope for the trans, if you don't then you're pretty much guaranteed to have internal problems.

 

[GM Guy]

ok, thanks ferm. we will unplug the harness and see if she will move.