HI,
New comer to Volvo land, just purchased a 93 960 wagon--decent shape, looks pretty good, runs well.

Here's the one issue, that I'm pretty sure it's towards the rear end.
On power--OK.
picks up a harmonic vibration at lets say 35-40 mph, an disappears when the power is off, or I apply light brakes.
Power back on--the vibe is back.
It isn't bad yet, and I'm thinking u-joint type vibe ( I am not sure it has any ) or rear wheel bearing-

Just need a little finger pointing or ideas where I should be looking first.

It's without a doubt a harmonic vibration, and prior to it getting worse I was wondering what in a general area to start--if this is a common issue.
First Volvo I've owned--but it can't be anything much different than any other vehicle--I just need some usual suspects--

Thanks,

Terry