My 2001 Jeep Grand Cherokee 4.7 V-8 shakes something awful sometimes when I brake at speeds of 50mph+. It then starts to wobble and doesn`t brake good. What is causing this to happen and how do I fix it? Any help would be greatly appreciated. Novice Mechanic, Joe Yuma, AZ

UNLESS there is a major front end issue the most common cause of the vibration is the rotors being out of round. this is easily correct by having a brake shop resurface the rotors. also the vibration could be coming from the rear as well. the way to determine if it rear or front is the next time you brake somewhere that it usually has the vibration try applying only the parking brake instead of the brake pedal. NOTE....when making this check be sure to hold the parking brake release button to prevent lock up of the brakes. the parking brake only works the rear brakes. this will determine where it is coming from. the back brakes will have either brake drums or either brake rotors. same philosophy but different operating mechanics. either way it can all be corrected by resurfacing the rotors and/or drums