I'm sharing Mike's question here, in case there are others experiencing something similar:

Mike said: "When i apply the brakes on a Geo Tracker it shakes a lot in the rear."

Here's the answer from one of our editors:

More than likely you have brake rotors or drums that are out-of-round, they may need to be resurfaced or replaced. If the brake linings (also called brake pads or brake shoes) are old and worn you should replace them as well.