ARBs new Air Locker(TM) Shim Driver is a professional automotive differential service tool for installing/servicing common shim pre-loaded differentials. Insufficient carrier bearing pre-load can result in premature bearing failure and ring and pinion failure in all differentials, and possible oil/air leakage issues in an Air Locker(TM) differential. Most common Salisbury style axle assemblies(e.g., Dana Spicer model 44) require the pre-load shims to be tapped into place in order to achieve the required pre-load during set-up. Tapping shims into a tight space from a single point on the outside edge of the shim can cause damage to the shim and render it useless, resulting in extra cost and labor to the installation. As part of ARBs new Air Locker(TM) Tools range of differential service/installation equipment, ARBs Air Locker(TM) Shim Driver is comprised of 6 different sized steel profiles designed to evenly distribute the installation force (from tapping) around the outside edge of a differential shim as it is tapped into place in the assembly. This allows thinner shims to be inserted into tighter places than would be possible without the Shim Driver.