Rear Clunk
 

I have a 2002 WS6 with a four speed auto trans. that has a clunk coming from the rear when stepping on the gas after or during a left turn, other than that there is no noise. This winter there was alot of work done, UMI sway bar, subframe connectors, and tunnel mount torque arm. The pinion seal, axels, bearings, and seals all replaced. another issue is a vibration when it shifts into overdrive. The overdrive issue was before all the other work was done. Looking for some direction, any help is appreciated.