rear end problem
 

Hi my name is randy first time posting sorry if i forget something..i have a 01 chevy 2500hd with a 410 rear end. Under load on take off rear end is slipping profusely. Once it gets rolling and into overdrive all is fine will cruise all day...also when i turn in either direction get a clanging sound bad took off the rear cover all gear look good no chips or breaks...any idea on what to look for ...thanx