Which bearings are you planning to change? If you disturb the running relationship of the gears by fooling around with the bearing fit, you're almost guaranteed to induce a gear whine. If they're not making noise, or there's excessive slack somewhere, leave well enough alone! Change the axle bearings and seals if you want to but that's all it's safe to do unless you have a LOT of experience building rear ends. I've been assembling rear axles for over 40 years, and I've only got about a 50% success rate with trying to install new bearings on a used gear set without creating unwanted noises.
Jerry
