Unless it's showing visible signs of leakage, stains on the pinion housing, etc., I'd recommend leaving it alone. It's very easy to upset the pinion bearing preload and induce a hum or rapid bearing wear, chasing gremlins that probably don't exist.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!