I just put a built 4l60e on my car that is suppose to be able to handle up to 650hp. Normal driving was fine for a day. I finally got out to test it at WOT and it doesnt want to go into 3rd gear at all and 2nd gear is delayed. My last tranny did some similar things. I had to hit the gas pedal 3 or 4 times for it to switch gears. Could it be the stall, gears, or is it actually the tranny????

 

where did u get it built? call them and let them no

 

Tuning is also an issue amongst other things, the rpm and the speed have to line up in order for the computer to shift the car. When i put in my 3.73's, I had to lower the shift mph because I was hitting the rev limiter before the proper shift mph.