JPW1

I have a 2001 A4 Quatro 2.8L manual. I would like to know what the cause and a soltution to the play in the drivetrain that is evident when shifting.

As I let the clutch out (even slowly) there is a thud in the rear of the car as the drivetrain engages. I can even get the thud to happen while the clutch is engaged - if I push hard on the gas and release quickly a few times By the third time I push hard on the gas, I get the thud in the back as the drivetrain engages. I also get rubber banding in stop and go traffic.

So far I replaced the front & back engine mounts, transmission mounts, rear two differential mounts all with stiffer rubber mounts from 034 Motorsports. Also replaced the clutch. This stiffened things up to about 75% of what it felt like new. But, I let a few people drive my car, who did not know how to baby it and now it is back to loose. Note that it feels better on cold days and when I first start out.

What is the cause of the looseness, the thud and what is the solution?
(Also wondering if the gears/differential are loose.)

Things that I have heard but not tried:
Replace the flywheel with single mass so there is not as much inertia
Install a stabilizing bar on the transmission
Install a urethane or hard rubber snub mount on front
Replace the subframe mounts (donut shapped)

Anyone who has solved this, please provide advice.

Nate (ETKA+Scumbag)

So why haven't your replaced the engine mounts, transmission mounts, and rear diff mounts? I would've started with those.

JPW1

"So far I replaced the front & back engine mounts, transmission mounts, rear two differential mounts all with stiffer rubber mounts from 034 Motorsports. " I also already replaced the clutch (because my mechanic recommended it). I replaced in kind with a dual density flywheel. After the replacement my mechanic commented that the old clutch did not look as worn as he thought it would be. I don't know if this matters, but even after the replacement, my clutch engages when the pedal is almost fully let out.

Nate, what would you try next?

Nate (ETKA+Scumbag)

When you say two rear diff mounts, do you mean ones like this:

http://www.avalonmotorsports.com/ind...roducts_id=168

JPW1

At the time of replacement, I was living in San Francisco and had no where to work on the car. My mechanic pushed hard to keep me with stock replacements and to stay away from urethane due to vibration and potentially more wear on the drivetrain. (He is conservative)

So I went with the O34 Street Density solid rubber replacements for all mounts listed. 034's description: "Since there are no voids or air pockets in these mounts, even though the rubber is only 10% stiffer, the resulting reduction in drivetrain movement is actually 25% stiffer than stock."

This sounded good at the time to bring things back up to where it was new. But it didn't quite get there and it quickly degraded. Note have always I baby the clutch, because I can't stand the thud. So no one else knows it is there until they try to drive it. Here are parts:

http://www.034motorsport.com/product...ducts_id=18141
http://www.034motorsport.com/product...roducts_id=773
http://www.034motorsport.com/product...roducts_id=772

Note: O34 also has the urethane parts replacement parts.
http://www.034motorsport.com/product...oducts_id=1214

awdehere

did your mechanic pull off the heat shield between the exhaust and the rear driveshaft? Your driveshaft center carrier bearing could be shot.

Bendy

I am dealing with the same problem. I have a 99 A4 2.8L manual. Here are the things I have replaced to try and remedy the problem:

-Greedspeed poly snub mount
-OEM motor mounts (old ones seemed fine)
-034 Motorsports street density trans mounts
-remanufactured driveshaft which included a new carrier bearing
-filled rear diff mount and carrier mounts (3 total) with 94 shore urethane from McMaster-Carr

I do have a Fidanza 15lb single-mass flywheel and was thinking that could be part of the problem since the heavier dual-mass would dampen drivetrain shock more, but since JPW1 has a dual-mass and seemingly the same problem, this cannot be the cause.

I believe I have a bad input shaft bearing as, after the car is warmed up, if I am in neutral at a stop with the clutch out, I can hear a ticking sound which disappears as soon as I push the clutch in.

Maybe there are some subframe bolts that are loose/rusted/broken? Maybe rust over time with these cars causes some weld in the subframe to let go? I can simulate the noise at a stop by slamming the clutch at idle, jerking the engine like I took a defibrilator to it, but since I've got all the mounting points attached, I'm not really sure what the deal is. Maybe my 1 year old driveshaft has failed somehow? I fear putting the car on jackstands and trying to jerk it too much. Maybe I'll do this put put a camera under it to record what's going on...?

We'll get this figured out one way or another! There's another thread going at AudiZine on this as well for B5's.

SilverUrS4

Also have the drivetrain slop in my car, new tranny mounts, engine mounts seem good. going to do the rear diff mounts this week hopefully that solves it. What is the procedure to check the driveshaft and carrier bearings??

JPW1

I got the Apikol Rear Differential Mount to add to my already installed O34 engine, transmission and rear differential mounts/bushings. The Apikol was relatively easy to install. The result was a reduction in thudding, which now sometimes occurs softly when engaging 1st & 2nd. The thud has stopped when getting on and off the gas. I notice more engine sound in the cabin and a just little more vibration. But for me it is worth it.

Note: with the brace and oem rear differential mount removed I could access and turn the drive shaft. I could rotate it about 1/2 inch and hear a clink in the gear box when it hit the end of the movement.

SilverUrS4

I installed new stern diff mounts and the power ring, didn't notice much difference. I then installed an 034 snub mount and bracket, it has made a significant difference in the driveline slop at the expense of more vibration. IMHO well worth the increased vibes for the tightness it provides.