Well I've been doing some reading and I'm not sure if it's the ABS module or the modified rear shims I need to fix this problem on our 96 850 turbo wagon. When braking the cars shudders or vibrates and it feels as if it is comming from the rear of the vehicle, although I can't be sure. It doesn't happen every time. However you can make it happen by applying extra pressure when braking. My wife says you can feel the pulsating through the pedal. After much reading I've narrowed it down to either rear pads that are not seating properly, in which case the modified shims might fix it, or the control module for the ABS system is bad or is going bad. The brakes were re-done by me about a year ago and have worked fine until now. The pads have plenty of meat left on them. Is there any way to know for sure whether it is the rear pads or ABS module? Thanks for any replies.