ewpvesper

Hello,

I just picked up an 02 Z28 A4 with 110,000 mi. I noticed under moderate acceleration a clunky sound and feeling in the rear. Recently under WOT at a dig i noticed the car just isn't launching like it should. The LS1 sounds like its normal and as healthy as it can be and it will rev up but the power isn't being transferred to the wheels, it feels like its stuck in mud. It will spin the tires a little bit and then won't take off. If i give it half throttle it will take off normally and go through all gears. If i WOT on a roll it will take off and almost have a "spike" in acceleration once its building speed. But if i take off from the "sweet spot" of 30 mph it will bog and build up and won't take off. Something is being limited. Also, if it drops to 1st sometimes it will bounce as it tried to shift into 2nd i believe and i have to let off for it to shift. I recently changed trans fluid and filter. Does anyone know what specific issue this might be? Thanks for your help.

ewpvesper

Bump..

Anyone know what this might be? Trans won't shift to 2nd under full throttle. Hits Rev limiter and shudders. Sounds like rear end to me.

clinebarger

Getting on these forums searching for a Silver Bullet doesn't always work!!

All anyone can do is try point you in the right direction.....Check all fluid levels, Check the Trans Mount & Torque Arm Mount for the "Clunk" noise.

Sounds Engine Performance related to me. Check the Fuel pressure, TPS, MAF, Secondary Ignition, Diagnostic Trouble Codes, Vacuum Leaks, Air filter, Fuel Filter etc etc.

mrvedit

Right. Such clunks are nearly always due to trans mounts.
And the trans will not cause spikes and bogs in the acceleration; these are engine issues.

ewpvesper

The engine has excellent power. The main issue is it not shifting to second under wide open throttle. I do have an exhaust flange leak after driver side cat. Easy fix but couldn't imagine that being a trans problem. Just changed MAF sensor and that took care of 02 codes. It just has a P0420 code prob cuz of that exhaust leak. I'll keep looking. Thanks though

ewpvesper

I think it's prob tps sensor. Thanks dudes. Gon try out two nite

ewpvesper

TPS sensor helped but still slips and shudders from a dig and at 30 mph. It feels like it the wheels can't keep up with the engine and feels like somethings going to break and then it hits a rev limiter. I'll try to post the video.

ewpvesper

Please see link. Thanks. Any help is appreciated

ewpvesper

https://ls1tech.com/forums/automatic...ift-issue.html

Sounds like my problem

mrvedit

Then you next step is to measure how much end play your servo has. The servo cover is on the passenger side.
While holding a ruler next to the cover, use a crow bar to press about 50lbs on the cover and estimate how much it moves in. 1/16 to 1/8" is spec; by 1/4" your band is worn and likely slipping in 2nd and/or 4th gear.

ewpvesper

im a total trans newb. So the band must be worn? Can i replace this stuff while leaving the trans in? I'll check for play tomorrow morning..

mrvedit

No, the trans has to come out to replace the band. At 110,000 miles it will need a complete overhall.
I have suggested and given instructions to members on how to lengthen the servo pin to get a bit more life out of the band. Some have gotten another 10,000 miles out of it, which gives a little to budget for a rebuild.

But lets start with that servo end play measurement.

ewpvesper

Cool..thank you, i appreciate it.

ewpvesper

i wasn't able to check the play yet i was thinking what would be the cheaper route. you think buying a new trans or rebuilding the one in there?

ewpvesper

Actually I don't think that is my issue because under WOT it doesn't go into second at all. But I suppose it's in the beginning stages of slipping because from a dig it just winds up and doesn't accelerate.