Well, I 4l80e swapped my trans am with the Frost harness and everything is working fine, but while I'm on the interstate at lock up, going up inclines, the torque converter unlocks for exactly 2 seconds every time. Also, it does it while it is cold out and I just start driving it (mornings going to school for example), except worse.
I'll get on the interstate, it locks up at 40 like commanded, but once I hit around 65 it'll unlock for a couple miles, then lock/unlock/ect. . . consistently. Sometimes it'll eventually hold lock up after driving it a while, but I have gotten off the interstate and ramped back on and it locks up fine again.

Bad sensor? In the tune? Brake switch?

 

Any of the above. You need to watch the commanded state of the TCC on a scanner and if determine if it's being commanded to unlock.

 

Thanks Jake, I'll do that.

 

When the car starts doing the unlocking/locking, I found I can stop it and make it lock up at all times by pulling my foot back on the brake pedal. This leads me to just adjust the brake light switch, but when I put it in cruise control, and it does it, it doesn't take it out of cruise control like actually hitting the brakes does. I wasn't able to have anyone tail me to see if my brake light flickers as it unlocks though. Do I need to replace the switch or just adjust it?

 

Some scantools also have pids which show the reason for TCC unlock.

 

Also check your tune.