Hi
I have this problem with the transmission in my Express 4.3 - transmission 4L60E. It won't engage second gear and I have to overdrive on 1st to shift immediately to third gear.
At about 25mph I have to take my foot off the gas to get the gear to shift into 3rd.
2nd gear does not engage under any circumstances.

Any ideas what could be the cause?

 

Unfortunately, the cause sounds like a transmission that is "going bad". Likely a failed shift solenoid, bands/gears/etc, are involved. If you are lucky it's just a solenoid in the valve body.

I wish that GM vehicle produced trouble codes for that kind of failure, like my Subaru recently did. Subaru has a Transmission Control Module (TCM) that is tied into the ODB2 system, and I was able to diagnose a failure to a failed lockup solenoid recently, and replace it myself for $50, versus the $5000 the dealer wanted.

I had a 2003 GMC Yukon with the 4L60E start having shift issues at 130k miles, and ended up having to have the transmission rebuilt.

 

Thank you for answer