In TunerCat I lowered the TCC engage and release in normal mode by 10 MPH in 3rd and 4th gears on my 1994 Z28. Now when I am in OD around 30 MPH third gear locks up, then right after that it unlocks and shifts into 4th gear. Right about that time I am at 35 MPH and fourth locks up. Why is 3rd gear locking up? I have never noticed it with the stock TCC settings. How do I fix this problem?

 

Without seeing your shift tables, I'm guessing, but if you lowered your TCC engage speeds by 10MPH, you might have lowered them below your 3-->4 shift point.

 

I did not think about that. But what my car does now is starts in first, shift into second, shift into third, third locks up for about two seconds, third unlocks, shifts right into fourth, then finally fourth gear locks up.

I think I am going to change the settings back to stock.