4L80e Stack shifting under boost?
07-25-2014, 07:27 AM
#1
4L80e Stack shifting under boost? On the street the trans shifts fine in normal driving conditions, and of course when you step on it, it just blows the tires off under boost. It's a 2k stall PTC single disc lock-up converter, and my "buddy" just "re-built" the trans. It's controlled by the Holley Dominator.
When we took the car to the track it felt like it just skipped 2nd gear. We looked at the data logs and sure enough it was only in second gear for maybe a 1/2 a second. We tried raising the shift points, rev limiter, etc. but every time on the 2nd gear shift it would hit the rev limiter and hang it in 3rd gear.
Any thoughts??
It is funny though because even skipping 2nd gear it went 148 mph in the 1/4. So I would like to feel what she'll do with all 3 gears and a decent 60'. Those times where on 13.5#'s of boost, 12* total timing, straight 93 pump, and driven 1 hr to the track on Mickey Thompson classic drag radials with a 1.76 60'.
When we took the car to the track it felt like it just skipped 2nd gear. We looked at the data logs and sure enough it was only in second gear for maybe a 1/2 a second. We tried raising the shift points, rev limiter, etc. but every time on the 2nd gear shift it would hit the rev limiter and hang it in 3rd gear.
Any thoughts??
It is funny though because even skipping 2nd gear it went 148 mph in the 1/4. So I would like to feel what she'll do with all 3 gears and a decent 60'. Those times where on 13.5#'s of boost, 12* total timing, straight 93 pump, and driven 1 hr to the track on Mickey Thompson classic drag radials with a 1.76 60'.
07-25-2014, 09:12 AM
#2
I built car for a guy about 10 years ago that had a turbo 400 in it. With a fresh trans it would have all 3 gears. After I would get on it one time it would kill the sprag and it would only have 1st and 3rd. We must have put 20-30 passes on the car like this. BTE shipped a new turbo 400 and we shipped the old one back. The cars only picked up 1/2 tenth with all 3 gears.
Your setup may respond different with all 3 gears.
It needs to be fixed regardless.
10-25-2022, 10:30 PM
#4
Okay, I know this is an old post 
but my turbo Camaro is doing exactly the same thing: Hitting the rev limiter in 1st gear and going straight to 3rd. It used to work okay--went from being a 9.70 car at the track to a 10.30 car. I want my second gear back at the track! Like yours, it shifts completely normally when street driving.
Did you ever cure your problem? I'd love to cure mine.
Thanks.
Mark
but my turbo Camaro is doing exactly the same thing: Hitting the rev limiter in 1st gear and going straight to 3rd. It used to work okay--went from being a 9.70 car at the track to a 10.30 car. I want my second gear back at the track! Like yours, it shifts completely normally when street driving. Did you ever cure your problem? I'd love to cure mine.
Thanks.
Mark
