Humming Noise = Bad Bearing?

[Mark R]

Classic rear wheel bearing noises. The fact that it "kind of disappears" at
higher speeds is indicative that other noises (wind, etc.) are masking it.
Theoretically you can loose the wheel if the bearing has a catastrophic
failure. In reality, I've seen them go a LONG time to the point of visible
wheel wobble at low speeds before being replaced. The sooner, the better,
however.
It's *possible* the noise if from another rotating component (brakes, CV
joints, differential, etc.) but unlikely.
A quick check is to grab the tire (further out from center the better for
more leverage) and try to move the wheel/tire in and out from the car. If
it's a new and slight noise, you probably won't have any play when the car
is sitting on it's tires.
Lastly, the rear wheel bearings are a common failure. I've replaced S4 rear
wheel bearings (same as yours) at 45K miles. Of course, that car was used at
a few track events per year. Audi sells a wheel bearing "kit" which includes
a new stretch bolt (must replace).
 Tools required:
Jack, Jack stand (obvious).
Tools for removal of brake rotor and caliper bracket (brake pad tools,
etc.). Air tools make the removal of the brake caliper bracket bolts much
easier).
17mm allen socket (this is for wheel bearing bolt).
Torque wrench (a common 1/2 drive 250 lb-ft will suffice).
Big breaker bar (really, this is an air tool kind of job.. I use *overkill*
a 900 lb-ft 3/4" drive air impact for these).
And a "hub shark" type of kit. I use the OTC kit. (I sell the OTC kit as
well as the Sir Tools B90 master kit or B90-VA VA/Audi kit for R&R of the
wheel bearings).
Alternatively, you can remove the entire wheel bearing housing and press in
and out the bearing in a press. But this is more work and you need an
alignment afterwards.
 With the right tools, not a terrible job.
 Mark Rosenkrantz

 On 10/12/05, mkb <mkb125 at yahoo.com> wrote:
>
> hey folks,
>
> On my 97 A4 18tqa, I'm getting a type of low, dull
> humming sound at around 50-60 mph, apparently from the
> rear. Kind of disappears at around 70'ish.
>
> Also, moving the steering wheel to the right effects
> it, i.e. noise goes away on right hand curves but
> comes back on straights and left turns?
>
> Any ideas?
>
> --
> mohammed
> 97 A4 18tqa
>
>
>
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