Clutch bearing, release or pilot ?

[denis]

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How to know if its the pilot bearing or the clutch release bearing need to be change. It make some bearing noise in the clutch housing from my 90 Audi 1988.

The noise stop below 950 RPM, and always makes noise more than 950 RPM, with clutch release or not (neutral or 1st,2,3,4 or 5 ).

I got a Bentley book but  see only 1 bearing not two !!

Tanks
Denis