Generation III External Engine LS1 | LS6 | Bolt-Ons | Intakes | Exhaust | Ignition | Accessories
Sponsored by:
Sponsored by:

Is this normal?

Thread Tools
 
Search this Thread
 
Old Feb 19, 2013 | 09:05 AM
  #1  
redlineshifter's Avatar
Thread Starter
Staging Lane
10 Year Member
 
Joined: Feb 2012
Posts: 61
Likes: 0
From: Easley, SC
Default Is this normal?

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!
Reply
Old Feb 19, 2013 | 09:18 AM
  #2  
LS-ONE_DAY's Avatar
TECH Fanatic
 
Joined: Jun 2007
Posts: 1,062
Likes: 2
From: Westminster, MD
Default

Sounds like it could be vibration from motor/trans mount(s)
Reply
Old Feb 19, 2013 | 11:17 AM
  #3  
redlineshifter's Avatar
Thread Starter
Staging Lane
10 Year Member
 
Joined: Feb 2012
Posts: 61
Likes: 0
From: Easley, SC
Default

Originally Posted by LS-ONE_DAY
Sounds like it could be vibration from motor/trans mount(s)
Normal vibration or need to be replaced vibration?
Reply
Old Feb 19, 2013 | 11:24 AM
  #4  
LS-ONE_DAY's Avatar
TECH Fanatic
 
Joined: Jun 2007
Posts: 1,062
Likes: 2
From: Westminster, MD
Default

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.
Reply
Old Feb 19, 2013 | 12:03 PM
  #5  
Grimes's Avatar
TECH Addict
iTrader: (3)
 
Joined: Mar 2003
Posts: 2,636
Likes: 2
From: Northern NJ
Default

Originally Posted by 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!
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?
Reply
Old Feb 19, 2013 | 02:06 PM
  #6  
redlineshifter's Avatar
Thread Starter
Staging Lane
10 Year Member
 
Joined: Feb 2012
Posts: 61
Likes: 0
From: Easley, SC
Default

I still have the factory pulleys and dampener, so assuming we have the same problem, changing your dampener wouldn't help.
Reply
Old Feb 19, 2013 | 02:07 PM
  #7  
redlineshifter's Avatar
Thread Starter
Staging Lane
10 Year Member
 
Joined: Feb 2012
Posts: 61
Likes: 0
From: Easley, SC
Default

Originally Posted by 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.
The car still has the factory mounts. Why stick with a rubber transmission mount? Will a poly just transmit too much into the cabin?
Reply
Old Feb 19, 2013 | 02:12 PM
  #8  
2000camaroSS2000's Avatar
Staging Lane
 
Joined: Apr 2009
Posts: 80
Likes: 0
From: San Antonio Tx
Default

same thing with mine, getting poly mounts
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

10 Reasons Daily Driving a Swap Project SUCKS! (& 1 Reason to Do It Anyway)

 Michael S. Palmer
story-1

6 Gifts Neither Your Dad Nor Grad Will Shove Into the 'Trinket Drawer'

 Brett Foote
story-2

Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

 Pouria Savadkouei
story-3

Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

 Verdad Gallardo
story-4

7 Most Reliable High-Performance Engines GM Has Ever Built

 Verdad Gallardo
story-5

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-6

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-7

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-8

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-9

Top 10 Most Powerful Chevy Trucks Ever Made!

 
Old Feb 19, 2013 | 02:25 PM
  #9  
Full-Force's Avatar
TECH Junkie
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (11)
 
Joined: Aug 2004
Posts: 3,070
Likes: 5
From: Upstate of SC
Default

rough idle, not that uncommon
Reply
Old Feb 19, 2013 | 04:36 PM
  #10  
dailydriver's Avatar
12 Second Club
 
Joined: Sep 2005
Posts: 4,273
Likes: 0
From: Bucks County, Pa.
Default

Originally Posted by redlineshifter
Why stick with a rubber transmission mount? Will a poly just transmit too much into the cabin?
Yes, the poly trans mount will transmit EVERYTHING into the cabin, including any/all driveshaft vibrations, AND rear axle and bearing noises/whine/vibrations.
Reply




All times are GMT -5. The time now is 10:50 AM.

story-0
10 Reasons Daily Driving a Swap Project SUCKS! (& 1 Reason to Do It Anyway)

Slideshow: 10 reasons daily-driving a swap project might not be for you. Or is it?

By Michael S. Palmer | 2026-06-17 09:39:05


VIEW MORE
story-1
6 Gifts Neither Your Dad Nor Grad Will Shove Into the 'Trinket Drawer'

Don't get dad new socks or a grill brush this year.

By Brett Foote | 2026-06-09 14:55:56


VIEW MORE
story-2
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

Slideshow: We take a close look at the ONE and Artidiag 800BT2 diagnostic tools from Topdon and the reasons to buy one over the other.

By Pouria Savadkouei | 2026-06-18 10:26:23


VIEW MORE
story-3
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.

By Verdad Gallardo | 2026-05-26 18:23:54


VIEW MORE
story-4
7 Most Reliable High-Performance Engines GM Has Ever Built

Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.

By Verdad Gallardo | 2026-05-21 16:45:27


VIEW MORE
story-5
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-6
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-7
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-8
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-9
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE