Greg,

Did they check your bushings? When you are making a hard stop the steer and tag axles are trying to rotate and move rearward. The only thing that keeps them from doing that is the radius rods that position the axles. Unless bushings have been changed sometime during the life of the coach they may be allowing movement that would otherwise be snubbed.

I think the same could be true of the drive axle, but in that case the axle cradle is supported at each end with air bags.