my 4L80E was dropping out of 4th gear when I would hit 55mph or 2500 rpm, I called TCI and they said check the pressure, I was at 75PSI well below spec of 150 to 175psi. so they said change pump. I installed a new pump and got 70psi. so I was told to change all the solenoids and the wiring Harness and vehicle speed sensor. I did all of that and the ruck drives worse than ever, it lags off the line and drops out of 3rd gear also and just revs up.

local transmission shop says I need a new tranny at 5k TCI thinks its electrical not mechanical. every shop around town just wants to rebuild it and I say if it reoccurs the same thing will my transmission be free. no one wants to diagnose or fix electronics they want to replace and if it is still electrically bad they want to send it out any way.

the truck is a 1996 k2500, with a 6.5 turbo diesel truck has 150,000 miles on it Transmission has 15,000 miles on it, new motor has 700 miles on it. I didn't need a new motor or tranny, I just wanted upgraded stuff. maybe once a year I might tow something but have never towed anything over 2000 pounds.

I am at my wits end