Audi A4 B6 2.5 Tdi Quattro Sport Avant Auto Rear Vibration

Quattro mad

Registered User
Here goes, bit of a saga.
I've have read quite a few articles relating to B6 owners experiencing similar problems to mine but haven't discovered the cause of the fault as quite often the conclusion or outcome hasn't been posted!
I have anAudi A4 B6 2.5 tdi QuattroSport Avant Auto with about 150k on the clock. About May this year I started experiencing vibration from the rear when I applied the accelerator. Initially is was intermittent but became more permanent & tended to be about 30 mph or greater. The first thing I did was to get my wheel balancing checked & I also get my 4wheel alignmentcheck twice a year. This made no difference. My Audi specialist mechanic suggested it could then be either the rearwheel bearings(which were ok) or the propshaft. Everything pointed to the propshaft, which he removed & thought it had excessive play in the centrecv joint, similar to what he had experienced with BMW's, which needed changing. I sent the propshaft to 2 independent propshaft specialists who rebuild Cayenne, Touregs & Q7 propshafts & both agreed the centrecv jointhad excessive wear which could explain the vibration symptoms I was getting. Unfortunately neither of these specialists could obtain genuine replacementAudi partsas Audi don't allow them to be sold individually on the open market even though my vehicle is 11 years old. I was left with 2 options, fit one from a breakers or pay Audi £1100 for a new one!
Not keen fitting one from a breakers, as it could be worse than mine, but I couldn't locate one anyway due to having an auto box, so left with getting it from Audi.
Got the propshaft fitted by my specialist on Thurs 7th Aug 2014 after waiting 7 days for it to be supplied from Germany. I drove about 100 miles & all appeared ok with no vibrations experienced. I was due to drive to York the following Tuesday, some 300 miles from home in Worthing. Split the journey & travelled some 200 miles to a Travelodge off the M1. All appeared ok. The following morning resumed journey to complete the final 100 miles. Travelled some 8 miles & got delayed in an accident for an hour & the car started showing signs of vibration from the rear end. This progressively got worse to the point the rear end vibrated every time I put my foot on the accelerator irrespective of the speed & stopped when I removed it. Exactly the same symptoms I'd experienced prior to getting the propshaft changed.
I reduced my speed down to 50 & limped into York. After leaving the M1 I pulled over & felt the rear discs which were very hot! My partner tracked down an Audi specialist in York who said bring the vehicle straight over which I did after navigating York's congested one way system to find our b&b.
The Audi specialist stripped down the brakes but said they were fine & he only experience the vibration once during the test run which he couldn't repeat. I collected the vehicle & drove it back to the b&b & left it there until Friday when I decided to give it a run out to Harrogate. I'd been driving about 6 miles when it started vibrating again. I took it back to the specialist where they experienced the same symptoms. They put it up on the ramp & checked the rear wheels, bearings, drive shafts but no sign of the cause & they didn't have the opportunity to strip things down.
Luckily I’ve got relay service so I got relayed back to Worthing yesterday as I wasn't going to risk further damage or cause an accident getting home.
I'm at my wits end & haven't thought about anything else during my stay in York much to my partner’s dismay & annoyance.
I don't think the vibration is caused by the rear diff as I don't get any loud thuds or noises coming from the rear which I would expect if it’s the rear diff. To me I think it’s the propshaft but it’s a brand new from Audi & therefore wouldn't expect it!
I'd really appreciate ant guidance or offers of advice obviously I'm going to get the propshaft checked out but I reluctant to take but vehicle to Audi just in case it’s not & get stung with a huge bill which I can't afford to pay!
 

Mike B

Registered User
I have the same model which has never done this .It has been to N.London for work by Adamms 24 on here(Chris) who is an expert on these and if it were me I would contact him.Dont like the sound of rear discs very hot unless something is binding or one disc is warped .Hope its not the prop or a diff.The seal on the centre diff has just been replaced after leaking for months and losing a lot of fluid but no vibrations
 

Spacemonkey

Registered User
I wonder if ti is anything to do with the 4wd system and traction controls? If there is a significant difference in wheel diameter due to mismatched or oddly worn tyres and the car is trying to correct it by using the brakes, thinking the rear axle is spinning? On Freelanders, they are renowned for messing up the centre viscous coupling due to slightly mismatched tyres- as little as 3mm can do it which could even be down to pressures. On them, newer tyre should go on the rear to counteract this, but shouldn't matter on the Audi system.

Could be a faulty sensor and again the car is trying to correct a fault that doesn't exist..?
 

seany26

Registered User
This could be the centre diff at the tail of the gearbox, I know it's not at the back of the car but it's situated more a less beside your seat, it could give you the sence that it's coming from the back of the car.
Only way to find out thou is stripping it off the gearbox. Check out Audi centre diff on Google and you may come across various cases with excessive wear.
With out experiencing the vibration myself it's hard to help you
 

Quattro mad

Registered User
Could be the propshaft again?

I had a similar symptom under heavy load - accompanied with a knocking sound.
The center bearing rubber was dead. Swapped for a 2nd hand one for £30 and it has been fine since.

Hi Guys,
Thanks for the responses. I think the problem has now been finally fixed but I wanted to leave it for a period of time before posting this response.
When I visited the Audi specialist in York they identified the n/s front inner cv joint was split on the front drive shaft & advised I should get the cv joint replaced before investigating the rear vibration. Audi don't sell inner cv joints just the complete shaft for £400, but I did manage to get one from GSF for £70.00 bit sceptical as made in China by GS-P who I'd never heard of. Anyway my Audi specialist in Worthing replaced it & the vibration has stopped!. I've now decided to get the o/s front inner cv joint replaced too, as they have both done the same mileage & I'm a firm believer that things should be replaced in pairs!
Just goes to show that vibrations can be difficult to pin point as they resonant down the chassis & where the vibration is felt, isn't always its origin!
 

Spacemonkey

Registered User
Good to hear! It's a shame we always discount Made In China as shoddy, but they do have excellent engineering skills- they make most of the small engines for Japanese firms and a heck of a lot of Japanese car/electrical parts which are then shipped back for that 'Made in Japan' sticker. Yes I do know that there is a lot of knock em out cheap and run merchants though.. And don't forget they make the best high speed trains, and no doubt will be helping out with this ridiculous HS2. I have been on they're high speeders and the quality far, far surpasses anything we can muster up! To be doing nearly 300kmh in almost perfect silence makes you wonder about the crappy trains we have here that require ear plugs...
 

seany26

Registered User
So I'm guessing the one that came off was shot then, did you get any pics of the old one.
 

Spacemonkey

Registered User
na, went straight in the scrap pile. The outside was caked in filth and old oil form the shock and you could see where the dust cap had polished the outside of the shock, and also the polished wear marks on the rod where it had gone in the shock! Both bump stops totally shot...
 
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