1999 V70 T5 rear brake hydraulic pulse/click

[aharres]

I've got a 1999 VOLVO V70 T5 with 195k miles on her. I've had a strange issue that I've had a lot of trouble figuring out. It's worth mentioning that I have the standard bbk (porsche 993 turbo front caliper, s60r rear calipers and rotors all around) and I can't remember if I was having this problem beforehand.

Every once in a while on moderate to heavy braking, I can feel the abs trying to modulate the rear brakes when it has no business doing so. I can feel (and hear) a single distinct click or pulse in the pedal when this is occuring and it seems to correlate with the wheel's speed (the period between clicks gets longer as I slow down). The strange thing is that it seems to be very intermittent. However, it seems to happen only when braking over a slight bump or rough patch in the road. I also pulled the abs fuse and the problem went away completely, so it's definitely something triggering the abs in at least one of the rear wheels (I haven't been able to determine which wheel or if it's both)