If there is a knocking sound coming from the rear of the vehicle, check through the following:

Check tray

Check rear tray hinge points. Ensure that all bolts are tight and secure.

If loose, retighten bolts.

Check shock absorbers

Check shock absorbers spherical bearings.

Check shock oil levels.

Replace as required

Check final drives

Check final drive mounting bearings for excessive play.

Check exhaust

Check exhaust mounting brackets - ensure they are tight and secure.