try installing part # 272272 shim kit for rear pads use brake grease also,

If the shuddering only comes at that last moment before the car comes to a complete stop, when you are slightly releasing pedal pressure, then try to bleed the brakes.

I had similar problem on my 855 recently. The brakes worked fine but just as the car was creeping to a stop, and I'm letting off on the brakes, the rear would shutter so badly that the entire car was vibrating. I bled the rear brakes, and got out some huge air bubbles. After that, all was fine.

Check the slider pins too...

Hi. I had the same problem. I found out it was in the rear brakes. To find the problem I pinched the hose to the brakes and did a test drive in a safe place, that told me which brake was at fault. The pins that hold the pads in were rusted, so I took them out and cleaned them up. The problem went away. Hope this helps.

Non-Volvo response, only time I had this was due to a warped disc, brake pedal pulsates during hard pedal pressure. If it's the disc, the symptom will be much more evident in a fast corner brake response. If only at slow speeds, I don't know. It is relatively easy to replace a disc but do both sides of the car and it is probably the front as that is where most of the stop occurs.