"The Manual" may be directed more to "Remove and Replace" than to "Theory and Understanding." This is some kind of Chevy/Workhorse/P3x-something, right? If so, it has "full floating" rear axles.
Full-Floating Axles use wheel bearings that are lubed by the rear axle lube. That's right, From the Differential. So if a Manual says to Repack the Bearings after a brake job that required pulling the bearings apart (some of the drum rear braked vehicles are like that, our 1983 E350 was), what you are actually doing is protecting the bearings from failure while the rear axle lube works its way out there. The grease you packed will be washed away.
Those bearings need to be adjusted. "Set Up" like front wheel bearings. The difference you'll see is that the spindle is hollow for the full float drive half axle to slip through. And the bearings themselves will be very large. There are also grease seals like front wheel bearings have.
Since its the rear axle lube that lubes the wheel bearings, it's essential that the rear axle lube be ***FULL*** and not contaminated with water, etc. If it isn't full, the lube will not slosh out to the wheel bearings on turns and that's how it gets out there!
My bottom line here is this. With the coach level side to side, check the differential oil lube. Make sure the level is at spec (may need a Manual), and stick a piece of clean white cloth in there. See how it looks. If the lube is full and clean, I'd be much less suspicious of a bad bearing.
