ARB RD99 - Manual (Page 7)

1 Introduction
5
1.3 Assembly Type Identification
IMPORTANT:
ARB’s RD99 Air Locker differential was not designed for use with the
factory standard Ford third member assembly (i.e., the original third
member produced by the Ford Motor Company to accept either 28 or
31 spline axle shafts).
Before proceeding with installation of this Air Locker it is highly
recommended that you ensure you have a third member assembly
which accepts tapered roller bearings of the dimensions shown in
Figure 1.
Figure 1.
Contact ARB or your local ARB distributor if you cannot determine
which Air Locker was designed for your application.
Also note that this document was written in reference to a standard
factory Ford type of axle assembly, and therefore, special installation
considerations due to any variations that might exist such as front
applications or high pinion and independent suspension models of
third member will have to be accounted for by the individual installer.