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Went out to the garage today to take my 1991 gmc 3500 4x4 up to the car wash and no reverse??? checked the fluid it was fine. Decided I would take it up for the wash drive was still working. On the way there I notice no overdrive?? I have the 4L80 E trans Does this sound like a mechanical problem or electrical? THANKS
Check the fluid level. Fluid pressure may not be enough. The reverse have a much higher line pressure than the forward gear ranges. Reverse Servo seal failure. A simple fix but since the transmission is out of the vehicle. They should do a check for other wear.
I was browsing thru the problems with the 4l80e and found a great site for the overdrive problem.
Visit:
www.454ss.com/Articles_new/red/4l80e_transmissions_problems.asp
I just replaced all the solenoids and have great shifts but no overdrive.