Search Ebay for "liquid moly" gear lube additive. It won't repair a worn out or pitted pinion bearing, but if what you're hearing is bear noise, it might quiet things down a little. You're probably giving a brain tumor patient an aspirin for his headache, however.
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!