Ok guys I took physical possession of my 88 LX today. She was awesome, and had alot of power. Anyway, she also annoyed the hell out of me. I would here a (my imtation) VUm vum vum vum out of the passenger rear. Are we talking about a wheel bearing? Thats all I can come up with!
I think 5.0Droptop is on the right track. A wounded axle bearing will normally give you some horrendous vibration. May as well pull the rear wheels off, pull the drums and have a look at the brake pads in the rear and see what you find.
Tires are pretty recent. So drum drag is a likely problem? I know nothing about these cars but will soon. It reminded my of a rear bearing issue I had with a grand prix. Is a spring not doing its job?
if you suspect brake drag, drive along at a decent clip and apply the e-brake. this will most likely change the sound/feel of the problem.
i have lost a rear wheel bearing and i thought the rear of the car was gonna fall off. the way i test for that is to jack the rear end up and use jack stands and all that. be real secure. then start it up (dont knock it off the jack stands when you start it up), put it in 3rd or 4th and you will actually see the wheel hopping around. i doubt this is it though.
id just jack up the pass side and give it a once over. check all moving parts. noises, esp from rear end, are real hard to diagnose, as the sound diffuses.
good luck and congrats on the new ride.
usually a wheel bearing gone intensifies the sound if you go into a turn...it will come in and out of the noise...
Like mentioned..jack the rear up and grab the tire, give it a tug with your hands at 12 and 6...Feel for play...