Loud LOUD noise at higher speeds

[97AUDIA418TQ]

I recently bought a used 97 A4 1.8T Quattro and when I'm driving it there is a very loud, loud humming noise coming from the rear. (The faster I drive, the louder the noise gets. At about 70 MPH the noise is so loud the radio needs to be at full volume to even hear the music) I assume this is because of the 'quattro' system but it is VERY loud and i'm wondering what could be causing this? Does something need to be lubed up; new bearings; or new something?? Any help would be appreciated greatly!

 

[excursion]

One of the rear wheel bearings has failed.

At the same time it's worth replacing the disks (if they are reasonably worn), as swapping discs involves removing the bearings.

 

[97AUDIA418TQ]

thanks!

 

[excursion]

oops ignore my comment about replacing the discs! This dosent apply to Quattro's /ubbthreads/images/graemlins/wink.gif

 

[Patrick]

One possible way to confirm if it is a wheel bearing and which side is to find an empty section of prefferably dry road and turn from left to right. In doing so has the effect of loading up each side of the car in turn where the noise should get louder when more weight is on the worn bearing.

I had an odd experience with my rear wheel bearing. Where the noise appeared without a doubt a wheel bearing at 40K then dissappeared within 100 miles for 10K? Then it came back first really faint for 10K and then became really bad as you descibe.

I discovered you can buy the same bearing kit (NOTE KIT) i.e. new drive shaft bolt and bearing from a general bearing supplier for 40% cheaper than the identical Audi kit. It is the same bearing - not a cheap alternative!

Agricultural places are very good at supplying bearings if your stuck for a source.

If your going to replace the bearing yourself you need a press with at least 4 tonne capacity and even this may not be enough without a little helping heat. If you are using a general press you have to remove the hub from the car which means you will upset the rear wheel alignment and you will have to have this re-established.

The reason I know about the press capcity is that I made a hydraulic puller for extracting the bearing from the hub while on the car. (Some dealerships have this - but it's a seriously expensive tool) I used a 4 ton capacity hydraulic ram and this bearly removed it. It's a seriously tight interference fit!

I'm going to upgrade my tool to a 10ton ram for the next time!