MEZERR

That's because light braking doesn't lockup the tires. As soon as you brake a little heavier, the rear tires lock up momentarily, and because you are in 4x4, the rear axle and the front axle HAVE to turn at the same speed, which causes the front to lock-up via the driveshaft, causing the bouncing in the rear.

dkushner

This sounds right. I noticed while in 4wd on both trucks. I'll play with it this winter so I can see the difference between 2wd and 4wd just out of curiosity.

redcelica

Does it do it if you put it into 4A?

OddBall

I experienced a similar issue with our old Expedition. It had TC, SC, 4WD...I was on an flat section of interstate with a very fine coating of ice, stop and go traffic with the 4WD in Auto mode. I let off the brake and with the slight crown in the road the truck became very confused for a moment because the crown caused it to side slip left and then move forward.

It was hard to describe but it kinda bucked a bit, stopped, bucked, stopped, etc...for the record the Expedition has 4 wheel independent suspension.

It sounds like you experienced something very similar to what I experienced.

As for the moaning noise it almost sounds like the ABS module was bleeding off brake pressure.