slight clunk sound in rear

[crazy5.0]

It's only when upshifting and starting off the line. I never had this noise until after I had to have my gears replaced and had a Auburn put in. My driveshaft is a aluminum FMS that's only 3 months old. The clunk only comes after 10-15 mins driving. Yesterday I jacked the rear up and put it on jacks and whiggled the driveshaft and spun it and there is no noise. I even ran the car on the stands and shifted gears and no noise. I also checked the upper control arm bolts and there tight,so is my exhaust hangers. The lower arms are only 2 months old and tight. When turning the wheels the driveshaft it does make a slight clunk when I first turn it and the there is a little play in the rear,but it turns freely and smooth. The gears themselves are quiet. The longer I drive the more advious the noise is. My rear brakes however do make clunks when braking in reverse.