i doing both to get a snug snug fit. i tried and tried and could not get that thing to stop rattling before the install. washers on the shaft and one in the mount. the dust cap deelly looks simalar to the gc top perch cap but a little smaller. it came off under the rear mounts with a thick washer. which i used both to take up space. i got a little confused during the long process at the end. my car rides rough. really rough. ive messed around with adjusting the front and firm feels the best. but the rear i think bounces like crazy. you feel the rear in the seat and the front in the wheel right?