Quote Originally Posted by 96lt4c4 View Post
So at what MPH are you locking and unlocking the converter in 3rd? How does this effect towing in 3rd?
My truck has 3.73 gears and 265/75-16 tires. I lock the TCC in third at 30 mph at zero tps and increase to 75 mph at 56% tps. It doesn't effect towing since the TCC unlocks with increased throttle. I don't think the GM TCC linings are designed to handle much torque so I wouldn't want to keep it locked with a lot of throttle, particularly with a 383 like yours. I also unchecked the flag that unlocks the TCC during upshift. I found it annoying when the TCC would unlock to shift into 4th and then lock again. The upshift with the TCC locked is not harsh at all.