This article is from the VW Technical FAQ, by with numerous contributions by Jan Vandenbrande others.
A: They'll make a roaring "wowowowow" sound, and the noise <NOISE> may change
depending whether you are heading straight or turning. Special tools are
needed to remove the bearing (cost ~150US$) though the bearings themselves
are around 30US$/each. Certain performance places listed above will sell
bearings packed with synthetic grease (last much longer, racing
applications).
 
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