Hey guys. My truck is a 95 GMC Jimmy 4.3, 4l60e, 154,000 miles with about 35,000 on rebuilt tranny. I changed fluid/filter about 6 months ago and added a big external cooler. Fluid looks good and doesn't smell burnt. I drove home from work this AM (25 miles) and truck was fine. Drove over to my parent's house this afternoon (about 20 miles) and tcc would not lock up. Looked on here and it said to check brake switch so I did and as far as I can tell it seems to be ok. Brake lights work properly. Other 2 things mentioned were tcc solenoid or worn out clutch in tc. I decided to go to town and get a tcc solenoid and fluid/filter and on the way there it locked up like it was supposed to. I pulled it down to 3rd and it locked up in 3rd. Drove around a while and then back home and everything seems fine. Could this be the solenoid on it's way out? What is the best way to check the brake switch? Thanks for any help.

 

It kind of sounds like it could be your forward sprag is still holding instead releasing in overdrive. Do u know if you got a new forward sprag when you rebuilt it?

 

No sorry the previous owner had it rebuilt. Is it possible it was just some dirt or something holding it up? I drove it today and it was fine.