Hi, I am new to the forum and I'm at my wits end in trying to fix the issues with my A4. Its a 2007 2.0L tfsi quattro avant special edition (217) with 87000 miles on the clock. Any help is greatly appreciated as I worry now that I have to drive my family around in the vehicle with the problems listed below. All of which started at the same time a number of months ago...

Firstly, when turning, the wheels slip at low speed, I have read previous posts into this and it appears to be normal for the quattro (diff related) however mine has become much more apparent, the slipping is quite aggresive now and I don't even have to be on full lock, it feels like losing traction on ice and gives the impression of the car lurching forward while trying to turn.

Secondly, there is a very apparent knock from underneath the car which can be vaguely felt through the steering wheel.

Thirdly, now and again at low speeds the steering wheel gets extremely tight but will continue to turn to full lock with force, and the steering wheel has even locked a couple of times and requires wrestling back to the dead ahead position.

Are these problems related? I have Audi telling me the steering rack is at fault, and I have an independent telling me its one of the two diffs, although he doesn't want to get involved with the job as he can't tell which one it is and could end up costing thousands. Both options are extremely expensive, but I need to clarify what the issue is before I start throwing money at it. Both garages have checked all the obvious bushes, suspension arms, basically anything they can access and have found nothing untoward.

Any help is greatly appreciated and thanks in advance..

 

I would take a look at your servotronic relay underneath your ECU. Also, have you checked your power steering fluid recently?

I'm not quite sure that it would be related to the differential problem. Is your traction control light going off at the same instance, the ESP(yello lit car with curvy tire tracks) light in your cluster. Do you ever notice the ECS light illuminated as well?

 

I have no lights illuminated and neither does the traction control warning light come on when the wheels slip! The power steering fluid level is ok and its appearance is normal. I did try removing the servotronic relay and other than making the steering extremely heavy, the slipping/knocking still persists.

 

Servotronic relay is under the dash not the Ecm box.

But your correct, that is what I would check first as well