Shock mounts stuffed???

[SPLINTER]

: Howdy ppl!

I have an AU2 xr8 ute and i was driving down one of those annoying multistorey undercover carparks and i felt the rear of the vehicle shuddering. I wasn't even booting it! I have also noticed this happens when i go down speed bumps really slowly and i was wondering if anyone else has had this problem and if they know what it is?
If it is the rear shock mounts how do i check them on a ute?
I have only had this vehicle for two months so it still has wty. I love it (venom red : ) but i have had a few nigly problems with it