wont shift from 2nd to 3rd @ wot

[todd]

have a 2002 chevy 4.8L w/4l60e that is in a 55 chevy. Trans shifts great at part throttle and at full throttle it shifts great from 1st to 2nd but 2nd to 3rd doen not shift. It will run up against the rev limiter. Had the computer modified origionally and then had the program relooked at, but they say the program in the computer is fine. Did have the trans rebuilt and did replace the 2 shift solonoids and the epc. Any ideas as to the problem.

[mrr23]

i had to firm up the shifts in the black car to get it to stop doing that.