My friend has a '97 3500 5-speed manual. He said that recently it started making a clicking/clunking sound in the drivetrain when it gets warm and he drives in 1st or reverse.

He did have the seals replaced in the rear end earlier this year and I am wondering if maybe they did not add a limited slip additive.

 

is it when driving straight? you wont notice the limited slip driving straight but it will show on slow turns and more in reverse.