Brake/Caliper Problem? Help

PLEASE HELP!!!
I drive a 1996 Volvo 960 Wagon that has had problems since the beginning of the year.
We were driving home from FLA and our car started vibrating (not the steering wheel) when we were going around 60 mph. We stopped at a service station (not a volvo dealer b/c it was Sunday) and after a lot of studying, they decided that we needed a new caliper on the left/rear. They replaced the brake pads and sent us home an told us to get a new caliper once we got there.
It continued and I went to the volvo dealer. They told me they didn't know what the problem was and they didn't think I needed a new caliper. I told them to replace it anyway.
Problems stopped for a little while, then it shook every once and a while. Went back and my brake pads were totally worn down. This was about 4 months after they were replaced. The Volvo service couldn't give me a reason why, but replaced them and charged me 1/2 price because they couldn't figure out what the deal was.
This past Saturday, the vibrations started again when I was on the highway and I brought it in. The right/rear brakes were hot this time, the others weren't. They say the caliper isn't worn and they don't know what the problem is. So, they are going to send me home without an answer.
If someone has an explaination or idea of what is wrong, please help. I talked to another volvo service dealer and they said that it sounds like a caliper problem... but haven't looked at it yet. Please help.

Did you ever figure out what it was, and did it vibrate when braking near a stop? I have a similar problem with a 93 940 sedan - a slight vibration when at highway speeds, but when the engine is warm, and the air temperature is 60 ish, I get a vibration when stopping, when it gets within 5 mph. Dealer cant figure t out

I may be able to help.

These are the facts.

1 the pads on the o/s/r brake keep wearing down.
2 That wheel was hot or brake was hot.

This may not be a problem with the brake caliper it's self seems it's been repalced but it may indicate a problem with the rubber flexible brake hose leading to the caliper. If the hose it's self is made up of 2 layers.
a steel brading on the inside & a rubber outer when the inner breaks down inside it is totaly un detectable from the out side.
What happens is it allows fuild to be forced down the pipe, but none to return which keeps the brake on ( Binding). Change o/s/r flexible brake hose. I hope this sloves your problem

I have a similar problem with my Grand AM 2001- I am now on my third brake job-the 2nd and now third were due to faulty calipers and it was not previously diagnosed correctly. The calipers become stuck on and the brakes overheat and can warp the rotors-which causes the bumpiness.

I hope you have it fixed now-I talke to four different mechanics before I got a complete understanding.

My 1990 Volvo 740 Turbo Wagon have the viberation problem whenever hit the brake after the service by Midas, they replace the new pad and resurface the rotor problem still there.

After I replace all 4 new rotor and brake pad (volvo pad) myself, the viberation problem solved. However I found the front right wheel still hot and caliper did not fully release after release the brake.

Finally found the guide pin on rotor (740 Turbo Aluminum wheel) cause the rotor off center cause the partial binding. I unscrew the pin, screw on lug nut bring the rotor back square then put the pin back only finger tight with threadlocker take care the problem.

pete