So my 91 TPI Z28 with my 700-R4 now unlocks properly when you let go of the throttle when on the highway. Why then it is necessary to have it also unlock when you step on the breaks? Aren't you already unlocked when you let off the gas?

Little confused,
Thanks.

 

So you don't stall when at a stop.

Tom

 

Actually that's not really the point I don't think. The converter should never lockup in 1st gear, so it shouldn't have a problem with stopping. My idea was that a converter should unlock with the brake because under an emergency stop the car should slow quicker if you are just slowing the car down and not trying to slow the spinning motor still putting power to the transmission and drivetrain and the car both.

 

I am pretty sure that the point of the lockup torque converter is better gas mileage. And the reality is that I have seen a lot of people with bad TCC that it will not unlock coming to a stop and will kill the engine (My part time job at an auto parts store for 7 years). You are right though that it shouldn't lock up in 1st gear as mileage in 1st and 2nd gear doesn't really matter to GM...

 

Ok guys, I'm still confused. If the TCC unlocks when you let go of the gas, why would it need to unlock AGAIN when you step on the breaks?

Thanks!

 

Actually, it unlocks when you step on the brakes...

 

it does not unlock just letting off the gas in 4th (OD)

 

Now I'm really really confused. I had a previous post asking if it's normal for my TCC to unlock when cruising on the highway when letting off the gas. The responses I got were that it was normal. And this is what I'm expriencing. I have a 700-R4 with a 350 TPI in front of it (if it matters). Now you guys are saying it isn't suppost to unlock when you let off the gas, only when you tap the breaks?

My tranny shop said it is normal as well for it to unlock when you let off the gas, but it just doesn't make sense why it would need to, and also I trust you guys way more than my tranny shop.

Thanks!!

 

The part that people have left out is that the TCC is not designed to unlock the instant you let off the gas.. It will eventually unlock (as determined by the computer), but not instantly. However, in a panic stop, you do want the converter to instantly unlock (cruising down the highway at 75mph, brick wall materializes 200 ft in front of you), hence the need for the brake switch override...