Sticks in first gear unless you let off accelerator around 2000 rpm. Wont stay in overdrive under a load. (Kicks into neutral) had scanner hooked up and shows tc unlocking in od under load. Abs light is on and vss code comes up on scanner. Tranny isnt slipping at all. Haul 10,000lb loads often in montana mountains with overdive off no prob. Has acted like this over a year. Bought truck from owner who said Transmission was rebuilt aprox 100,000 miles ago...

 

The first thing to do is fix the VSS code. That can cause all of your problems.

 

I swapped the vss on rear diff with a good one from my buddys truck and its doing the same thing. Anything else i can check?