We just went through this. Had both tires on the back axle on a 2006 Cougar 30' bumper tow that were wearing on the inside. The passenger side was the worst. One spring on the passenger side had come unpinned, and the spring leaves were no longer stacked vertically. The passenger side rear axle spindle was bent. The RV store said that they have not had good luck bending axles as they seem to be prone to rebend later.
We upgraded both axles from 4500 to 5200 pounds, the axle sets came with new hubs, brakes, bearing, spindles, etc.
The new axles were installed and checked for hanger spacing, all was within specs. Had new springs, shackles, and equalizers installed. ALL of the bolts have grease zerks for greasing the suspension.
The old shackles, equalizers, and spring ends were shot, they should have been replaced four years ago.
So, just a tip to consider replacing the factory suspension components with upgraded, greasable, heavy duty upgrades.
We've put on a thousand miles since last week when we had the axles replaced, and the RV seems to tow much better.