Recently bought 1999 GMC Jimmy 4.3 with 4L60E. Purchased the vehicle knowing that I would have to let off the gas to let it shift into every gear when driving. Example would be that I would start in first let off the gas for a second and it would go into 2nd and so on... Well I tried to drive out of a parking spot the other day and nothing. Would not move. Checked fluid and it was empty. Filled it and found a leaking cooler line. Fixed the leak put a quart of Lucas trans fix in and nursed it to auto zone to top fluid off. Now it won't shift out of 1st. Not with the pedal or manually. Any help would be greatly appreciated.

 

Also the Speedometer, Tachometer, Reverse, Neutral, and Tow/Haul work. My research is leading me in several different directions but nothing definitive.

 

Looks like it will go to the tranny shop so I don't throw parts at it without knowing the cause. Will post the findings to help anyone with this problem in the future.

 

It's dead, Drove it when very low on fluid. The inside is destroyed