Try driving a few miles before doing anything else. The most common reason for a loose pinion nut is a deteriorated bearing behind it, and as soon as you tighten it, the bearing will get really noisy, really quick. I'll be surprised if you get 10 miles without nasty noises, and/or a pinion nut that's loose again.
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!