Hard Brake Vibration

[Maine240]

Hello,

I have tried the search feature with little luck. So I will post, 92 240 wagon with 187,000 miles. Purchased used with 130,000 about 6 years ago. The current problem is that when breaking at low speeds a very hard vibration occurs and gets worse as the speed decreases to stop. I have had 4 sets of rotors on the front in the past 2 years and just replaced the rear set Tuesday thinking that was the problem. I attribute the first 3 pairs of front rotors to cheap autozone rotors until I finally bought ATE brand from a volvo parts supplier last Christmas. I just put the summer skins back on and the front rotors looked fine while the rears were worn enough to replace. The vibration seems like it stars in the rear because it shakes the tailgate and then in the seat then makes its way into the wheel as I come to a stop. Just before the stop the vibration is very harsh. Could it be wheel bearings? The wheels do not noticably shake when jacked up. The only other characteristic is that when driving at low speeds, say below 35mph I can hear a low frequency hum or harmonic. It is not faint and should be considered. Any help would be much appreciated.

Thank You

[jimmy57]

Have the bushings on the rear axle that fit where the lower trailing arms bolt to axle. Also inspect the other links to rear axle. The motion in rear axle when these fail can let braking twist the axle to point that it causes vibrations from the excess angle of the rear universal joint. The speed of this vibration will be "faster", i.e, several beats per wheel revolution. A brake rotor vibe is slower as it usually is one beat, maybe two, per wheel rotation. U joint vibe is more like 6 beats per wheel rotation.

[Maine240]

I had the car on the jack today, noticed a small audible knock when I shook the wheel at the top. Shook the trailing arms and they didnt move however the bushings are original I suspect. I did notice when driving it the moan begins at low speeds whether or not the brakes are applied or not. I can slow down from say 50 to 30 and the moan radiates throughout the entire car and is very abrupt. After searching the forums I decided to put it in reverse and really accelerate and I got a constant thump from under the seats. Center support bearing failure? I am thinking the rear wheel bearings as well?