Our 94 850 wagon has this vibration that occurs JUST as we're about to stop, sort of the sound you would get going over a drawbridge or those 'sleep bumps'. It only does it when it's dry outside, and always the 3rd or 4th stop after leaving the house.
I removed the rear brakes yesterday to inspect, and made sure they had the 'cutout' shims on them. They did, but there was no grease on them or the back of the pads. The pads were about 60% left, looked ok to me. The rotors looked fine too, so I greased everything and put it back together. The first trip out, the car did the vibration thing again. It's not a vibration you would get say, if the rotors were warped (I've had a couple of cars before with warped or bad rotors) There's also no squealing or any other sounds whatsoever. It only shudders just at the stopping point.
Could it be the front pads? Would a complete brake pad change, all with the proper ABS grease, stop the problem or should I look at something else?
I didn't inspect the front brakes yet, I had searched this and other forums to find that the rear brakes seem to be the vibration problem. Any advice appreciated!

 

Try removing all the abs sensors and clean them and then drive it and see if it happens again.
Also try to pay close attention to what happens.

Do you feel it in the brake pedal?
Do you feel it in the steering wheel?
Do you feel it in the entire car?

 

Thanks, will do...

I know FOR SURE, that we feel it in the whole car. The brake pedal is perfectly smooth, as is the steering wheel.

I'll clean those sensors, put new pads and shims all around, and post back.
I appreciate you help! Many thanks -
P

 

If it still happens after that it is the rear rotors.On some occasions the rear rotors will slightly warp and cause a noise that will sound like a huge deap Bass sound echoing through out the car.

 

I'll take a look at that too.....

Thanks again Tech!

 

Your welcome let me know how it goes.

 

Ya my 97 850 has crazzzyyy vibration once they front rotors heat up or when i have a load in the car...i resurfaced the rotors and changed the pads, and it went away for a while then it came back. It just a pure vibration going through the whole car, and almost seems like bass. But i'm pretty sure that its my rotors, even when i look at it from an angle they are like blue (warped). Anyway good luck with your let us no what happenes

 

Have you checked the rear rotors on your car?
The rotors you cut were they Volvo rotors?

Volvo rotors don't like to be cut and will vibrate after cutting them.

 

i believe they were aftermarket...but i cut them because they were vibrating, so it went away for a while aftering cutting them then it came back one day when i had heavy load in my car, and when the weather was really warm. the rear seemed fine they just make noise...but its obvious that its coming from the front, when i brake and they start vibrating , if i apply more pressure to the pedel it kind of goes away, it almost seems like when theres only about 75% pressure on the pedal it does that

 

Next time it happens see if you feel it in the steering wheel or the brake pedal.

 

no vibration to my steering...or directly to my pedel...it seems more of the chassis to me but definetly from the front end

 

Not to sure then I know when the rear ones doing it the noise can fool you.Sounds like it is coming from the front of the car and not the rear.
Also does it do it all the time or just after it gets pretty hot after driving for about 20 to 30 minutes?