# '02 GMC 2500HD 8.1L Allison Transmission



## alivings (Jan 9, 2008)

Last season I had problems with the shift sensor and points? in the Allison transmission in this truck, they had to be changed twice during plow season. Has anyone else had any problems with this transmission? The dealer that i took it to told me that i needed to make a flange and put it over the sensor to block the snow from landing on it. This sounds like something the dealer should take care of, but i went to two other dealers and they told me there was no recall for this. I'm just curious to see if anyone else has had this problem.


----------



## snow game (Sep 28, 2008)

I have an 01 in my fleet, I only had a problem in real big storms, it has happened two times to me, The first time I parked it my garage and put a torpedo heater on it, the second time it wouldn't shift at all so I removed both battery cables left them off for about 5 minutes and put them back on then it ran like like new. 
The reason I put the heater under it the first time was because there was too much snow frozen to the bottom of the truck, I figured I would have to see what I was working on so I threw the heater in there. The 2nd time it happened I was driving through my yard through very deep snow to get to a machine that had to be jumped, but because of the rough terrain I couldn't plow into the machine. Both times tranny was working fine prior to driving through large piles of snow, so I knew it couldn't be anything too big.
Don't ask me what made me think of taking off the battery cables (I'm ashamed to say its usually the way a fix my computer too), just lucky I thought of it.


----------



## B&B (Nov 4, 2006)

Its a very very common problem with the NSBU switch on the early Allisons. The dealer should have installed the updated (and better sealed to the elements) switch. Possibly they did...the second time.


----------



## snow game (Sep 28, 2008)

I didn't bring it to the dealer either time, both problems happened very close together and the dealers are never opened during a storm. I suppose they could have done an upgrade when it was in for other issues (they did injectors twice at no cost) and didn't tell me about it.


----------



## alivings (Jan 9, 2008)

Thanks guys, I'm hoping this doesn't happen this year, i'm down to just this truck and it will be costly. I'll try to keep it in the garage and the transmission dry when not in use.


----------



## B&B (Nov 4, 2006)

You can change to the later style, better weather sealed switch if you want. Not very expensive and not tough to change. There is a thread here from last season with pics and everything on the procedure to change the switch.

Then the truck wont need to live a sheltered life.


----------



## alivings (Jan 9, 2008)

Thanks for the help, i found the thread and will be swapping out the switch.


----------

