Rear diff/wheel bearing noise

Hi guys

I recently had some of the interior out of my Reimo camper to get the rear carpet replaced and whilst driving it down to my coach trimmer (across town) I noticed an oscillating wob wob wob type sound coming from the rear. 

I've had the car up on a ramp with the rear wheels spinning up in gear and it seems difficult to tell if its wheel bearing or diff related. There doesn't seem to be any play in the wheel bearings using the usual 12 and 6, 3 and 9 o'clock method, but it does seem to be coming from the wheels, but on both sides?! 

Are these vans prone for knocking out wheel bearings? (bearing in mind it's a fully laden camper) 

And if its not wheel bearings, if its the diff that's noisy then is this something I can just live with for now (the van gets used for occasional local weekends away, but will be on a 2 week trip in August) If not, what's the prognosis for repairs? Big job or not? 

The noise is there at all speeds, doesn't seem to change when loading into corners etc, doesn't seem to go even if I coast out of drive in neutral, so I was thinking more wheel bearing related? 

Any advice much appreciated. 

Thanks, Simon.

To replace the bearings you need to pull the half shafts, cut the old ones off and drift/press new ones on. To do this you need proper big boy garage tools, press, slide hammer for a start.
I'd try replacing the diff oil and see if that helps.

Cheers Clive  

Replacing the axle bearings isn't a problem, I have a rather large big boy garage to play in  

I'll try the diff oil first though cheers.