I have a 2001 8.1l with the Allison Transmission. I have owned the truck over 5 years. The Allison failed at 100K and I had it rebuilt at a cost of nealry $4000 3 yrs ago. I curently have 174K on it and at 112K the rev started popping out of gear. In most cases it gets me out of a parking space but most times I need to shift from N to R several times to make my rev moves. I obvoiusly have lived with it for queit some time but I really like the truck and the engine has giving me no problems. I want to keep the truck but putting in another $4k to a rebuild would not make sense. Hopefully some one know whats wrong and it is a quick/cheap fix.

I've always been a chevy guy again love the truck but I'm disapointed in the Allison having these problems Ive owned 1/2 tons with over 200Kmi towing 4-6lbs before with no failures.

Thanks

Tom

You may have a bad NSBU switch-- it is worth a try. Lots of problems with the switch in 01-04 Allisons when it gets in water and snow because it is exposed to the elements.

Thanks for the info it sure seems like a good place to start. Is there an online place I can buy the NSBU swith?

find a local Allison Dealer and get it from them. A lot cheaper than GM.

Got an 02 diesel doing the same thing with similar miles.