GM Torque-Converter Lock-up

TandW · 10-31-2009, 01:20 PM

Yesterday morning after refueling the tranny didn't do the lockup in any gear for the rest of the day. Now today it is working properly. This happened mysteriously in the same way several years back. Is this just a mischief nite thing that will go away? Anybody know?

DriVer · 10-31-2009, 07:30 PM

Chief, I expect that you could always call one of our sponsor service centers for a little chat about the issue. They won't bite and they know these systems.

oemtech · 11-01-2009, 07:13 AM

I will assume that you have GM tranny and not an Allison. There is a solenoid in the trans that runs the lockup function. The usual malfunction, when the solenoid goes south, is the lockup does not drop out. I replaced one years ago in a Monte Carlo SS I had with an after market version for $35, GM want $75 for the same part.

OBTW - The solenoid is accessible by dropping the pan.

TandW · 11-01-2009, 10:11 AM

Oemy, thanks. I have the 4 speed GM tranny. I have done very little towing and generally travel lightly and never at the speed limit, as I have the J71 AAPB that requires travel in the Granny lane. Again it is that the converter refused to lock-up. And on a restart the following day it operated normally. Now on my '95 Yukon the lock-up went out and never came back even after trying some Seafoam along with fluid change. The mechanic said some 7 years ago that the solenoid on the Yukon was internal and relatively costly to repair. As it wasn't really using much more fuel and had become a "back-up" vehicle I have chosen to drive it as is, since it also saw service in northern Maine and Franklin County NY and the metal has been sheeting away. I suppose that my concern with the tranny in the motorhome is that is this the way that all GM trannies go? I've got nearly 400,000 miles on the '88 Sierra pick-up and it still works purr-fect.