If your truck equipped with a 2-piece rear drive shaft and you're raising the rear of your Superduty, then this driveshaft alignment kit may be required.
When you lift the rear of a Superduty with a two piece rear driveshaft, most trucks will experience, what we refer to as a (shimmy) or vibration out of the rear when accelerating from a stop. This usually occurs from 5 thru 20 MPH and the faster you accelerate the worse is is. Using the carrier bearing shim kit to lower down the position of the carrier bearing will normally correct the shimmy/vibration.
Depending on how tall your vehicle is lifted and the length of the driveshaft this kit will may or may not fix all the shimmy/vibration.
This is what Jack-it has experianced over the years correcting this condition:
Crew Cab long bed trucks you can eliminate the shimmy/vibrations up to 2-6 inches of lift and get rid of most of the shimmy/vibration with 8 inch lift
Crew Cab short beds you can eliminate the shimmy/vibrations up to 2-4 inches of lift and get rid of most of the shimmy/vibration with 6 inch lift
Ex-Cab Long beds you can eliminate the shimmy/vibrations up to 2-6 inches of lift and get rid of most of the shimmy/vibration with 8 inch lift
The other cab and bed configurations should have a one piece rear driveshaft.
If you have more lift than what the carrier bearing shim kit will correct we recomend a one piece high strength driveshaft. You can call Jack-it at 888-452-2548 and we can help you with that if needed.