cfair

I have a 99 Z28, 4L60-E. At WOT it runs through 1st, barks second and runs all the way to the rev limiter without shifting to 3rd. During normal driving it shifts to 3rd fine. I bought this car used and it has been doing this as long as I've owned it. Changed the fluid and filter but that didn't help. Any input from the tranny gurus would be greatly appreciated.

Chris
Jacksonville, FL

jimmyblue

iTrader: (11)

Stock WOT 3-4 upshift on my car was set to 125MPH.
If you hit the rev limiter before 125MPH then you are
hosed. I believe this may have been a trick to prevent
the 3-4 shift under full throttle (it's prone to hurt the
trans I think, it is not torque managed either in the
stock tune). Higher ratio gears or more converter slip
would only add to the shortfall (MPH vs RPM).

cfair

My problem is between the 2-3 upshift, somewhere around 80 mph or so.

Chris
Jacksonville,FL

exstanger

iTrader: (4)

Does it hit the limiter or is it just real close. Mine hits it on occasion but rarely. If you bought it used someone may have used a handheld programmer like the hypertech and messed around with the shift points and not moved the rev limiter up enough. No real way to find out without talking to the prev. owner though. You may could find out from a gm dealer or a tuner. Not real sure about that though.

cfair

It just bangs on the limiter. I've never used a programmer but that was my first thought, that the shift pont may have been programmed higher than the rev limiter. This didn't make sense to me though, but luckily another active thread on this board is talking about the same problem. I'm going to go hunting for a VSS this morning. I'm out of town right now, my gf is a bridesmaid in a wedding, but while she's doing the bridesmaid/bride prep thing I'm going to try and get out and wrench on the Z/28. We'll see how it goes.

Chris
'99 Z/28 | 4L60-E
Jacksonville, FL

blkZ28spt

Your tranny might be in trouble. Seach the auto trans section for your problem and 3-4 clutch pack failures.