rel3rd

iTrader: (43)

(sorry for originally posting in tuning sub-forum)

Car is a 2000 Trans Am, turbocharged 6.0 with a 4L80E swap.
Factory 2002 Silverado ECU with 3 bar SD tune (done before I got car)

As soon as car moves...as in less than 10 feet or so, it shifts into 2nd gear...

No matter how I set my shift points via HPTuners, the transmission shifts 1-2 as soon as the car moves.
If I manually put the shifter in 1st, the thing bucks like crazy

2-3 and 3-4 shift seem fine in factory GM ECU aided shifts during "normal" driving, or if manually shifted

2-3 manual shift at WOT (or close), under boost, shifts great, and instant.

Transbrake holds in 1st gear, and lets me rev to just over 3000, but I have not let go under boost/load, due to the way it acts, in regular old normal 1-2 attempts...

It also unlocks converter very easily, in OD, for some reason.

Original tune and my revised transmission tune both uploaded below.

I may try to do a complete "do-over" of the entire transmission settings today, using a stock 2002 6.0/4L80E Silverado, since that is the ECU, that I am using in this car.

"Stock" tune had gear ratio set at 2.73 for some unknown reason....(speedo was reading WAY HIGH as well)
"Revised" tune has 3.73 gear ratio, since that is what the car actually has...(Ironically, speedo reads LOW now)

Car has 3.73 gears.

01ssreda4

iTrader: (96)

How did you do the electrical portion of the swap?

rel3rd

iTrader: (43)

Unfortunately, that's an unknown.

Wiring down on the transmission definitely appears to have been altered. Shifted weird from Day 1 (My Day 1 is only about 2 weeks ago, when I got the car)

It had a bad shifter cable that was loose in it's bracket (the one at transmission side, broken tabs on cable). I replaced and adjusted the cable, figuring that was the whole problem...but it is exactly as it was before.

As soon as I have an extra set of hands, to drive the car, I was going to use the HPTuners VCM Controls to see if I can force it to stay in 1st.

I'm half tempted to just convert it to a manually shifted setup, since I have no idea what/how anything was done...and the previous owner was almost as clueless as I am on this thing...

rel3rd

iTrader: (43)

Thinking about just getting one of those manual control boxes from James since he has a black Friday sale in them today

01ssreda4

iTrader: (96)

Is the front input speed sensor plugged up and working? Foggy memory but I believe even holding 1st the 80e will force shift second (at some point), whereas the 60e does only as commanded and will let you hold it to the limiter. I tried it once and it grabbed second with the shifter still in 1st. I used the Nelson harness for my swap and it seems to be working well.

rel3rd

iTrader: (43)

Everything is connected. As to if it's all working?

This shifts, immediately, almost as if it's 1/2 way into 2nd while sitting still, if that makes sense? As soon as car begins to move, 2nd gear. I tried to hold it and about went through the windshield it bucked so bad.

Well...i went ahead and ordered the Manual Control Box from James for 150 bucks. If that "fixes it, at least I know it's something wrong outside the $5,000 transmission and converter...

jimmyg

2nd on a 4l80 is limp mode . Look and see if the plug is wet. If not it is probably electrical in nature

rel3rd

iTrader: (43)

It ended up being the input and output shaft sensor plugs being plugged into the wrong ones...switched them and it works great now.

The guy I got the car from recently had the engine freshened up and had some shop reinstall it, and the transmission...

Thanks for the replies