Four rear axle housings are used in the early Falcons. Three different
size ring and pinion gear sets. The 6 3/4-inch gear is used only with the
2 and 4 door sedans, with the144 cid. The 7-inch gear is used only in taxis,
Rancheros, and station wagons with 144 cid. All models with the 170 cid used
the 7-1/4 inch gear. The sedan uses a 2.440" wheel (axle) bearing diameter.
Taxi, Ranchero, and station wagon had a 2.677" wheel (axle) bearing diameter.
Three types of differential case are used. The
two-window type is used only in 2 and 4 door sedans with the 144 cid, and is
used in this housing only with a 3.10:1 ratio. The one-window case and the
two-piece case are used in all four housings in all combinations with various
Two sizes of differential case pinion and side
gears are used in all three cases. The side gears are not interchangeable as
between the two-window case and the other two types.
Pinion gear thrush washers are also not interchangeable. The side gear thrush washers, however, are interchangeable between all differential cases.