First let me say that I now there are many posts about TC's so this is probably nothing new. I have a 97 Suburban with a 4L60E(rebuilt with about 30K on it). About 3 years ago the TCC PWM shorted out and blew the fuse and was replaced. Sometime after that, the TC(torque converter) intermittently would unlock and lock back up going down the road. Would usually stop after a couple of times and not happen again for weeks or months. Also when this would happen the cruise would not work. Recently I noticed that it would take a little bit of time for the TC to lock up, since I drive 3.5 miles to work and never get above 45mph(traffic permitting) this was not an issue. Have went up north hunting a couple times recently and noticed that the TC very seldom locks up now???. Replaced the brake switch - no change, swapped out the TPS(from junk yard) - no change, swapped cruise control module -no change, last night changed the TCC PWM -no change. Going to take it to a trans shop today, but does anyone have any thoughts? Never had the TC shutter, seems to shift fine, when the TC would lose lockup it was at a steady speed or sometimes after letting off the gas. Kind of at my wits end and don't want to keep throwing money at guessing what is wrong.

 

Wire coming from the brake switch was broken. Looks like it was broken inside the jacket. Think when I pulled the harness to unhook from the switch I finished the break. Was lucky to see the broken wire. There is a reason I hate electrical and intermittent problems, they are hard to track down.