redlineshifter

Hi,

I have an 02 z28 A4 w/ headers, no cats, SLP loudmouth, lid, ported TB and tune.

When I'm sitting still with the car running (in gear or out makes no difference) I feel a shake through the bottom of my seat every few seconds. The idle speed on the tach never changes (600 rpm) and if you are outside the car you can't see the car shake or hear a miss, but it always has that shake through the seat every few seconds.

I don't have a whole lot of experience with V8s so is this just something these cars do with open exhaust or should I be looking for a problem?

Thanks!

LS-ONE_DAY

Sounds like it could be vibration from motor/trans mount(s)

redlineshifter

Normal vibration or need to be replaced vibration?

LS-ONE_DAY

Depends on the motor and trans mounts. If they're rubber they may be cracked/old and need replaced. If they're poly/solid it's normal. Rubber (stock style) vibrate the least/absorb the most, poly is in the middle, solid transmit the most vibration because they don't allow flex.

If you do need them replaced, most people, including myself, advise poly motor mounts and a rubber replacement for the transmission mount.

Grimes

iTrader: (3)

I get this too, mine is an M6. It drives me nuts sometimes. Mine is very slight, and I was wondering if it had to do with the underdrive pulley I'm running. No i'll effects from the vibrations as of yet though. I may try throwing on the stock dampner and see what happens.

Do you run an aftermarket dampner?

redlineshifter

I still have the factory pulleys and dampener, so assuming we have the same problem, changing your dampener wouldn't help.

redlineshifter

The car still has the factory mounts. Why stick with a rubber transmission mount? Will a poly just transmit too much into the cabin?

2000camaroSS2000

same thing with mine, getting poly mounts

Full-Force

iTrader: (11)

rough idle, not that uncommon

dailydriver

Yes, the poly trans mount will transmit EVERYTHING into the cabin, including any/all driveshaft vibrations, AND rear axle and bearing noises/whine/vibrations.