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1996 GMC Yukon wont shift to third


I have a 1996 GMC Yukon and this morning, it began skipping third gear. Well actually it wont shift to third, it just revs high, but never engages third. Any ideas what’s causing this?

I assume you have the 4L60E transmission. These transmissions will default to second gear if the Power Train Computer discovers a fault. Usually, the OD OFF light will flash or the check engine light will illuminate. Have a transmission technician scan the computer for codes. That will lead you/him toward the likely problem.

Let us know what codes are found and what repairs were necessary to solve this problem

Yes, its most likely the 3/4 clutches. The 3/4 stack up in these transmissions are a very weak point. Whenever I rebuild one of these I always upgrade the 3/4’s amongst other things. The first thing I would check is with a scanner. We need to know whether the computer is commanding third gear. Its not going into limp mode. Limp mode in one of these transmissions is defaulted to 3rd gear, so most likely the problem is mechanical. I like to cover all bases anyways.