the rear end gears should not whine. Whining gears are a sign of a botched install. Also once rear gears start whining, there isn't much that can be don't to correct it since the tooth pattern is established in just a few miles of driving. You're going to need a new ring & pinion plus a bearing kit. Expect to pay about $250-$300 for parts and about $250-$300 for the install.
