[mmracing95]

I have a 4l60-e gmc tranny and it works fine until you drive for awhile or are driving about 60 for ashort period. You stop and when you start again upshifts are hard almost slamming into gear. Funny thing if you stop at the next light turn off the truck for a few seconds then restart it and go again, it shifts fine for awhile again?????

[wretched ratchet]

If you will post this question in the Transmission-Rearend Thread, you will get more qualified viewers and better response- - - - and Welcome to the Forum

[Crosley]

Originally Posted by mmracing95

I have a 4l60-e gmc tranny and it works fine until you drive for awhile or are driving about 60 for ashort period. You stop and when you start again upshifts are hard almost slamming into gear. Funny thing if you stop at the next light turn off the truck for a few seconds then restart it and go again, it shifts fine for awhile again?????

Mileage on this trans? Any recent work or fluid service work?

Is the check engine light on?

Any vibration , or engine mis-fire? Or something that may feel like that

when you cycle the ignition key off , then re-start the PCM is reset possibly from a DTC , so the trans works well till the PCM sees a problem again.

I would suggest a scan of the system with a proper scanner, not a code reader. A code reader may pull some codes out that are useful

[oldbogie]

Originally Posted by mmracing95

I have a 4l60-e gmc tranny and it works fine until you drive for awhile or are driving about 60 for ashort period. You stop and when you start again upshifts are hard almost slamming into gear. Funny thing if you stop at the next light turn off the truck for a few seconds then restart it and go again, it shifts fine for awhile again?????

I start by suspecting either or both the Throttle Position Sensor (TPS) located on the engine as part of the EFI; or the Electronic Pressure Control solenoid (EPS), this is inside the tranny pan, have developed a temperature related failure.

Be assured this needs to be looked at, hard shifts will eventually start breaking expensive internal parts.

Is the Check Engine Light coming on? Codes may help narrow where the failure originates.

Bogie