Just had a new auto trans put in my old 12er. Truck runs and shifts fine if I drive it normal. Taking off at about 1/4 to 1/2 throttle, truck goes thru the gears perfectly. Lock up works fine. If I drive the truck hard- and have fun, truck won't shift unless I let up on the pedal. I have to left off well past 1/2 throttle so the truck will shift. First to second is perfect under full throttle. Its the shift from 2nd to 3rd that the truck won't make under full throttle, or almost full throttle.

 

Check the throttle cable
http://www.dodgeram.org/tech/transmi..._lever_adj.htm

 

hey thanks for heads up. Thats a pretty simple fix. I won't get to try it until the morning, but the alignment was off. Once I was able to figure out how to work the button, it was easy. I had the local trans shop scratching there heads. They kept saying its the valve body or its internal. Just wasn't adding up. The trans is brand new, works fine at low speed, but when you hammer on it, all of a sudden the internals are bad- yeah B.S> . Its so hard to find a good mechanic with a brain, that won't rape a guy on price, and really has a full understanding of things