HELP - Rear vibration 1.8T Quattro

[BigG]

Hi All

I'm really hoping someone on here can help me out with a problem I have discovered.

When accelerating between 60-70 in 6th gear on the motorway I get a really odd vibrating through the entire car from the rear.

I have also noticed it does the same in 5th and 4th. When accelerating at around 2500rpm.

It does not happen in 1st, 2nd or 3rd gear.

I've recently (4-6 weeks) had a Milltek exhaust fitted, however it didn't do this straight away after fittment. It's only been noticed in the last few days.

Currently have 77'000 miles on the clock.

It's a 2004 A4 Saloon S-Line 1.8T 190 Quattro.

Also had it remapped. It's recently had a new set of coil packs and a new clutch (both from audi).

Anyone experienced this before ?

Any help would be much appreciated.

Thanks

Graeme

 

[ScottyP45]

propshaft or driveshaft knuckle couplings maybe? used to be a common source of speed related vibrations on all RWD cars back in the day...

 

[BigG]

Would that not be noticeable in 1st, 2nd and 3rd gear too though ?

My problem only appears to happen in 4th, 5th and 6th @ 2500rpm.

 

[chasdrury]

At a guess one of the tailpipes is rattling on the bumper....

Mine does, just haven't it fixed yet!

Chas

 

[BigG]

The vibration is from the rear but I don't think the back bumper. I can feel it through the entire car, but it appears to be coming from under the rear seats.

I did have the tail pipes re-alligned last week as one was not perfect in the gap.

The car is under audi warranty until July this year, but I'm not sure they will cover it now I've had the exhaust fitted.

 

[ScottyP45]

The prop is running at final drive i.e. road speed and it gets faster the higher speed you go, not what gear you are in - but try doing the same speed in any other gear, it should still vibrate if its a prop or driveshaft.

If its actually RPM related, I would look at the engine and gearbox mounts maybe.

Did they have the propshaft off to do the exhaust? It might not be bolted up true - so its now vibrating.

Or they left one of the prop flange bolts out...

 

[Q4]

Hi Graeme,

I have exactly the same issue with my quattro a4 and have been trying to get to the bottom of it.

What I have found is that basically my rear diff is shot! As you probably know our quattro system is permenant 4 wheel drive, unlike the haldex system used on TT's and A3's, therefore if it has had different depths of tyres on front and rear axles then this can cause the rear diff to "wind up" and cause excessive wear on the crown and pinion. This wear can be felt physically by hand and measured by rotating the propshaft from side to side and the amount of "free play" is known as backlash.


I have gone back through my service history and noted on a couple of occasions that new tyres have been fitted to one axle and not both at the same time as required.

This of course may not be the problem with your car, as stated before it could be an inner or outer rear CV joint or even a rear diff mounting gone soft. Obviously if this has only happend since the exhaust has been fitted then checking it for fowling on the car / drivetrain would be the first port of call.

Hope this helps and you get to the bottom of your problem.

Regards