Some cars experience rear wheel hop or judder under accelleration.  

The causes and cures:

Aged (hard) tires.
  • Replace tires

Excess clearance in the lower hub carrier bearings, wheel bearings or inner control arm bearings.

  • Check and adjust bearing play.  See here and here.

Use of urethane or other soft bushings in place of the OEM bearings.

  • "Revert" to standard tapered roller bearings.

Soft upper subframe mounts

  • Replace mounts (Jag steel sheetmetal cage), or bushings (ERA tubular cage)

Too-soft damper settings or worn dampers.

  • Set the dampers as described in the manual.  The adjustment is a small screw near the bottom.  You can experiment by going significantly stiffer on all 4 dampers to see if that effects the hop.

    If it seems like the damping is significantly soft with more than 5 clicks off soft, you may have a bad damper.  That can only be checked effectively by removing the damper from the car and removing the spring from the damper.