Chris2000 3/18/2010The hesitation can be a an engine control sensor like a tps switch, or any number of other possibilities. When you say hesitates and Jerks can you be more specific, it happens when you accelerate from a stop, it happens when you are cruising at a constant speed? The loud noise when youstart the car can you pinpoint where the noise is coming from? under the vehicle the engine compartment? and what does it sound like? is it a loud whinning or a squeal? What were you doing when you inspected the rear when you felt the tap, where you doing a bounce test? pushing up and down on the bumper? Sorry for so many questions, but answers will help start to figure out your problems.