Agree with most posts above, in particular the casters, looks like they are right out on the tail of your track and will cause this. I too have seen the same things on my 900. Your shocks may or may not need rebuilding but as pointed out above, the rear torsion springs hold up the back of the sled not the shocks. Deal with your springs for the sag issue. Shocks resist the cycling of your springs but don't actually hold up anything (unless of course they are charged or air shocks like W/E or Fox floats) I believe the 900 shocks you would have in there are simple hydraulic shocks that do not contribute to your sag issue.
Hope this helps.
Hope this helps.
