It helps decrease the angle of the differential input shaft. When you lift the rear, the driveshaft-to-input angle is increased... in other words, there's more angle at the U-joint between the center driveshaft and the input of the rear axle housing. So the higher you lift the rear (as in: the farther away the axle is from the chassis) this angle increases.Nice build! Looking to do the same set up to my rear suspension and was wondering what the benefits\difference is by adding the 2.5 degree axle shims are? Thanks ahead of time
To high of an angle can cause more drivetrain noise, weird vibrations, premature u-joint wear, etc. The shim helps tilt the front of the axle housing (and thus the input shaft location) upward to decrease the angle, to help prevent the issues I just mentioned.
EDIT: A lot of people try shims if they get weird vibrations/noise at certain speeds (even with stock suspension); I did not have any of the issues, I installed the shims as a preventive measure since I was taking the rear suspension apart already when doing the upgrade.