Absolut Quattro

I have an '02 A4 with 104k miles and lately have noticed a humming noise which sounds as if it were coming from the passenger side front wheel. I have some experience with wheel bearings going out in an old Acura of mine and the sound is similar. It is noticeable above a comfortable radio volume. I have been paying attention to my tires of late and have not noticed uneven wearing yet. My tires have about 60% tread left so I eliminated that from being the source of the noise.

Is my initial assessment correct?... any help would be greatly appreciated!

tonyj

If the sound changes when you turn slightly from one side to the other I would guess wheel bearing.

Absolut Quattro

Another question... is the wheel bearing generally sold as a hub unit, or just the bearing? I got a price from NAPA and they sell the complete hub unit for right around $100. Also, is this a job that I can tackle myself to save $200 in labor costs? I have some experience as a mechanic at a garage, but are there any particular tools needed to change this assembly? Thanks!

olaf

You need to disconnect the two upper control arms, the steering rod, the two lower control arms, and remove the axle nut. Then you can remove the upright aluminum suspension assembly. You need to bring this to an auto machine shop and have them press out the old bearing and press in the new bearing. You need an M12 12 point to remove the bolts that secure the bearing flange to the upright. It is a pita job, but do-able if you are willing to put in the effort.









You should also get the bearing kit so that you get new bearing bolts (in case you strip them) as well as a new axle bolt. The axle bolt is a stretch bolt that you are supposed to replace.

The total cost for my repair was $124:

$91 for the wheel bearing kit from German Auto
$25 pressing of bearing at auto machine shop
$8 for some new hardware and blue loctite

As for special tools, you need the following:

M12 12 point for bearing bolts ($10-35 for a kit depending on quality)
17mm hex for axle bolt removal (Sears sells a hex for $8 or buy a 1/2" drive socket key)
ball joint puller - makes the job much easier (there are nice ones on Ebay for $25 that fit Audi's)
a long 3-4 ft pipe and/or breaker bar to torque the axle bolt properly

I actually did the job without the ball joint puller, but it would be easier with the tool. Also, my joints were not seized as my car is an '05. If you have an older car with higher miles, the joints could be more problematic. I have heard of many stories where people have to cut the upper cinch bolt to remove the upper control arms. I was able to remove my bolt with a little motivation. I re-used most of my hardware, replaced some of the crush nuts and used loctite blue for extra measure.

Finally, this is a good time to inspect your drive axle and replace the CV boots if they are damaged. You need an M10 12 point to remove the 6 bolts at the transmission.