Axel Noises, 90 240sx

[skylinekin]

Ive been hearing loud clunking noises when I go over bumps, if I pull either of the axles towards the diff and let go of them they will spring back towards the hub with a loud clunk, the same clunk I hear when I hit bumps. How do I fix the noise? Is there something i need to tighten, or do i need to buy some new axles? this is on a 90 240sx with a stock open diff. Thanks.