Volvo: Volvo S80 AWD Rear Shimmy

Question
My 2004 S80 AWD had a shimmy in the rear end.  

It occurs most when I am accelerating up hill and is much worse when I add passengers to the rear.  

Shocks and sway bar links appear to be fine.  

Thank you,

Chris B

Answer
Interesting ,firstly i would remove the driveshaft and drive the  car .Possibilities would be the
driveshaft joint stiff or starting to seize .There are problems with the rear awd unit but this does not sound like that .Let me know what happens when you drive without the shaft ...