I have a 4L60E transmission in a 98 Z71 pick up. The problem is that when I am riding down the road, it shifts 1st, 2nd, and 3rd, then the engine revs and wont shift into 4th 9overdrive)... is there a simple fix for this or do I need to rebuild the entire transmission?
Thank you!!!

 

Probably one of these:

1. Band is worn.
2. Servo problem - a worn seal or cracked 4th servo piston.
3. Bad Valve body

How many miles does the vehicle have on it?