Justin_2000z28

so i installed a set of aam 4.10s and after i took it easy on the car to let the gears brake in. but after a good week i put it in 1st and got in it and shifted to second . got to about 5500 rpms put it in 3 and all it did was bounce off the rev limiter. did another 45 roll floored it in d and it went thought 1st shifted into 2nd, went all the way through and bounced of the rev, i let out of the gas and got back in it. it shifted fine
it only does this at wot. and it shifts from 1st to 2nd like it has a shift kit.
any advice ?

ROCNDAV

iTrader: (100)

did you reprogram your computer for the new gears?

Shift points will need to be readjusted with the new gears.

Justin_2000z28

Not yet , I should be getting a tune for graduation.

Ian Johnston

I am a little slow, but why does the computer need to be reprogrammed after a ratio change? I understand to reset the speedo, but doesnt throttle position/load, and engine RPM dictate gear changes to a point?
Sorry for the dumb question, but I am no computer expert.

mrvedit

You are correct. If you don't care about the speedometer, you can can change gear ratios and/or tire size without changing the tune. Basically RPM is the input shaft to the trans and speed is calculated from the output shaft of the trans and obviously the ratio between them is the same. Speedometer speed is a multiplier of the output shaft rpm.

Part throttle shifts are actually programmed from the Speedometer speed.
WOT shifts occur when BOTH the programmed speed AND RPM are reached.

Therefore the OP's problem is not a missing tune. (Going from 3.23? to 4.11, his speedometer is reading much higher than actual.) The reported harsh 1-2 shift indicates the PCM has detected a problem and is setting max line pressure. It should still be shifting at the same rpm and speedometer speed as before.

OP:
The first step here is to scan for codes.
Other than the harsh 1-2 shift, this unfortunately sounds like a failing 3-4 clutch. But start with a scan. If that is OK, tell us more. How old is the trans since its last rebuild? What RPM is the 2-3 shift occurring at? Is the car accelerating at all after the 2-3 shift or immediately revs to redline?

Justin_2000z28

It's never been rebuilt as far as I know. I'm only the 3rd owner. But it's accelerating, them it's like it won't shift it hits rev limiter like there more gear to go. But when it started acting this way I had a bottle of Lucas stop slip and I put it in it. And and some ATF and fixed the problem for now. But I'm just going to take it easy. at the end of the summer I wanna make mine a 4l65e with a shift kit.

Ian Johnston

Thanks for that. OP, was this problem there before the ratio change? I would be interested to see if going to a higher numbered ratio has any affect on shifts. My pickup is running a 4.56 diff, and although my trans possibly has a shift kit, it has a harsh 1-2 shift as well.
I am looking at going to a 4.11 or 3.7 to bring the revs down a bit.

Justin_2000z28

It has always been rough shifting 1-2 since I bought the car a year ago. But it just started this problem after the 2.73- 4.10 swap. But it didn't look like there was much fluid and I put that stop slip in it and some ATF. But as far as I know the transmission has never been takin out.