Knocking CV's indicates excessively worn grooves on the bearing races.
  This is a sign that someone has neglected to clean and repack them thousands of miles ago.
  They can be disassembled, cleaned, inspected, re-assembled and repacked, then re-installed so that they will rotate opposite the direction that they have been previously.  This causes the balls to ride mainly on a different side of the race from where the worn spots are located.
  This will buy you lots more time, until you can afford to replace them all.

HTH,

Mike B.
  ----- Original Message ----- 
  From: Jarrett Anthony Kupcinski 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Monday, November 30, 2009 7:00 PM
  Subject: knocking noise on acceleration

  I've started hearing a knocking noise from the rear of the vehicle
  when I accelerate. I'm thinking this is a sign that I need to clean
  and repack the CV joints (which I've never done). Does this sound
  right to anyone with experience?

  Of course, the joints might be worn and in need of replacement. How
  would I tell if they were worn beyond their service life?

  Thanks for your help.

  Jarrett Kupcinski
  89 Westy, Oly