Hey all, My dad has an 01 2500hd, Truck has 245k on it, Transmission has never had an issue ever, He changes fluids every 30k, This morning He left the driveway and truck would not shift out of 1st gear. It has the Allison 1000 transmission. He turned around and went home, Restarted the truck and it works fine now.

It has never done this, Only info I found was a possible sensor that could be crapping the bed.

Any info is appreciated.

Thanks

 

He also just told me he first accelerated it acted like it was in neutral, he then put it in reverse and the light that says r on the dash flashed. He shifted to forward then back to reverse and it worked. Then it would not shift to 2nd gear. He turned it off and it has work fine since. I'm thinking neutral safety switch?