FirehawkNS

I will try to explain my question. I bought my 99 Z28 last June. I had a 94 camaro before that and a 87 Firebird before (just for some history with my cars). When I got my 99 I noticed that when you let off the gas (at lets say 50 mph for example) the car has a nice back pressure and rpms slowly come doen like any car I have driven. But when I but on the brake its like the car goes into neutral. The RPMS drop to idil speeds (like 1000 rpms), if I let off the brake it goes bake to normal rpms. Also if I leave the car in 2nd or 1st (Good for letting the engine slow the car down when on icy roads) when you let off the gas, instead of letting the engine slow the car, the trans goes to a neutral state. My Question is, is this normal. My 94 didn't do this nor did my 87. But both were V6's. I do have a HPP3, but the car did this before I had it. Any suggestions since I am taking the car to the dealer monday for some other problems and my warrenty has 1000 miles left.

Mikie

Dang Nick,
Not really sure about that one , but I will bump this up to the top of the page for others to comment on.
Come on guys you have heard to symptoms now give us your diagnosis.

Later
Mike

PhantomTA

they will do that... i dont know if yours is doin it more than normal or not?

My GS does that.. its normal with the loose convertors in those cars

kjlvilla

I may be able to explain some of your symptoms. At highway speeds, your torque converter clutch (tcc) comes on. In 1998 GM put a calibration into the pcm called an ECCC (electronically controlled capacity clutch). What this does is keeps the tcc on when you take your foot off the gas. Older systems used to unlock the tcc with 0% tps, then when you would reaccelerate the tcc had to engage again, giving a bump on and off. The ECCC gives you a seamless decel then reaccel, no tcc bumping on and off. This is why you get more engine braking with newer models, your torque conv. does not slip like it used to. When touching the brake on ECCC or non-ECCC cars, the tcc always releases, that is why your car feels like it neutrals, you are feeling less or no engine braking from the torque conv. Your highway speed question seems normal.
As for no engine braking in D1 or D2, your overrun clutches come on in manual ranges and lock the (I think) forward sprag race. This prevents the sprag from overrunning and gives engine braking. If your overrun clutches are not working, you would never know it except for no engine braking in manual ranges. In D1 your low and reverse clutch comes on and locks your low roller to prevent overrunning in addition to your overrun clutches.
So, you probably have one normal condition and one clutch pack that needs to be checked. Hope this helps.

FirehawkNS

That was one well written explanation Kjlvilla. Thanks. I just got the car back from the dealer yesterday for another problem and they said that they tested the transmission and they said "nothing abnormal was noted". Guess its ok. Thanks for the help everyone, even you for trying mike .

Later