This problem would usually show up under the passenger side.
Your in the right spot for problem on your side their should be a plastic shim for a space between the spring and bolt or shaft for spring to be mounted to chassis frame, you may see it on the passenger side since no noise.
In
this link you will see a link to Workhorse information, not sure he covered this noise problem of many he has fixed. the new shim you should be able to get from Altra Parts.or Brazels. On mine I forced a plastic flat rib in space between the mounting bolt and looped spring.
Workhorse search ===
Here is what your looking for.