tachometer slipping?

[tom klein]

this is on an '02 legacy wagon, with 5-spd mt.

under heavy throttle i noticed that the tachometer suddenly dropped
from about 4200 back to 3500. i hadn't shifted, and i didn't feel any
lurching from the engine. everything else seemed normal.

is this clutch slippage (possible but i haven't noticed any other signs
of it), or is there something in the tachometer that might slip like
that?

 

[Kevin Hall]

If the clutch was slipping under power the revs would go up, not down.
KH

 

[Cliff Top]

Alternator belt slipping?