Hard Knock from Undercarrage

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02-21-2012 | 05:55 PM

Parkerboy

Thread Starter

1st Gear

Joined: Jan 2012

Posts: 8

From: North Carolina

Hard Knock from Undercarrage

I believe my differential is causing a knocking sound. Has anyone had an issue like this before? is this a costly fix?

02-21-2012 | 05:58 PM

M5S5

Tech Certified

Joined: Jan 2012

Posts: 1,167

From: Eastern Lawn Guyland

Front or rear of vehicle can it be heard?
Over bumps ?
When accelerating or decelerating?

Think we need more info to go on for help to be offered.

02-22-2012 | 04:19 PM

Parkerboy

Thread Starter

1st Gear

Joined: Jan 2012

Posts: 8

From: North Carolina

the knock is coming from the rear. it happens during acceleration after a gear change, sometimes if i accelerate quickly it will give me a slight knock as well

02-22-2012 | 04:51 PM

bmoore98A4

1st Gear

Joined: Jan 2011

Posts: 249

check your diff fluid and for shaft play. In my old tahoe after towing our boat the rear leaf springs streched and would produce a knocking/metal on metal sound. Granted that a tahoe is not an audi haha

02-22-2012 | 05:01 PM

M5S5

Tech Certified

Joined: Jan 2012

Posts: 1,167

From: Eastern Lawn Guyland

I would check you center support bearing on the driveshaft. It will clunk on acceleration & shifting.

02-22-2012 | 05:22 PM

Dozanti

1st Gear

Joined: Sep 2010

Posts: 327

From: Ravenna Ohio

Don't forget to look for cracks in the subframe, missing bolts, or broken subframe mounts !
BMW e36 body styles are well known for this, seen it a few times on audi's as well

02-22-2012 | 05:53 PM

bmoore98A4

1st Gear

Joined: Jan 2011

Posts: 249

My center support bearing is on its way out

These quattro systems are basically LSD correct?

02-23-2012 | 08:15 AM

chocalotstarfish

Super Moderator

Joined: Dec 2009

Posts: 4,298

From: USA

Rear diff mount. Replaced mine last year. If when you shift and stomp on it it sounds like the hooker in the trunk is kicking the floor boards that's it.

Got mine from Ringer-Racing.com super easy fix about 35 mins.