I've got what to me sounds like a bearing whine coming from one of the rear wheels. It's got all the symptoms - changes with road speed etc.

It's in the garage now, rear end on stands under the trailing arms simulating on road conditions. However, I can't simulate load on the wheels and this is the question - with on road loads exterting much more pressure through the bearings, is it reasonable to assume I won't necessarily hear the whine if I can't load the wheels when stationary?

The wheels feels smooth when I turn it by hand and has the normal tiny in-out movement at the top, but I can't tell if the bearing is worn. I listened using a long screwdriver against my ear and can't hear anything obvious either.

I have no problem changing the bearing and probably will just to be sure.

If it is the bearing, I think it's probably only just beginning to have problems, unlike a really knackered bearing that would have much more obvious symptoms during garage tests.

Is this a reasonable assumption?

 

In my opinion, yes.

If the bearings are on the way out you should be able to hear a slight grinding noise when the wheel is not under load.

On the other hand if you hear absolutely nothing it can be the diff as well.

 

I just checked the symptoms again - the in-out movement was more than I originally thought (maybe I didn't do it hard enough the first time).

I got underneath while it was being jiggled and I saw the hub move while the half shaft didn't, so I'm now confident it's definitely the bearing.

 

If you don't hear a grinding noise from the bearings it may be you can still adjust them to the proper settings, so just tighten them up and do the same test again. If you can hear any grinding noise coming from the bearings after the adjustment you're in for replacing those bearings with new ones.