Thanks. I'll google that. Haven't adjusted a TPS since I owned a 5.0.

 

You're going to have a whole new set of problems if you try to adjust your tps. The tps also controls the shift points, you'd have more going on than just no lock up if it was the tps. My truck would lock up at random times when driving. Like when my foot would hit the side of the brake pedal.
The brake pedal switch like I said controls the lights through one set of contacts and the tcc through another set.

I guess since the tps is easier to get to you'll start there?

 

It's the misfire tables. You need to desensitize them and run them all up to 32,767.

 

Why do you think its locking in 3rd?

 

Because it is. Doesn't slip at all sometimes, have to lay into it to get it to unlock. It's VERY obvious when this thing is locked and when it's not.

 

It certainly is possible to tune the TCC to lock in 3rd gear.

 

I don't know about trucks, but the factory tune on f-bodies enables lock-up in 3rd and 4th gears. So your tuner may have left it that way or decided to tune it that way for some reason.