Front Axle
FRONT AXLE - 248FBIDESCRIPTION
The Front Beam-design Iron (FBI) axle consists of a cast iron center casting differential housing with axle shaft tubes extending from each side. The tubes are pressed into the differential housing and welded. The axles is equipped with semi-floating axle shafts, meaning that loads are supported by the hub bearings.
The differential case is a one-piece design. Differential bearing preload and ring gear backlash is adjusted by the use of shims located between the differential bearing cones and case. Pinion bearing preload is set and maintained by the use of a collapsible spacer. The stamped steel cover provides a means for inspection and servicing the differential.
OPERATION
The axle receives power from the transfer case through the front propeller shaft. The front propeller shaft is connected to the pinion gear, which rotates the differential through the gear mesh with the ring gear bolted to the differential case. The engine power is transmitted to the axle shafts through the pinion mate and side gears. The side gears are splined to the axle shafts.
During straight-ahead driving, the differential pinion gears do not rotate on the pinion mate shaft. This occurs because input torque applied to the gears is divided and distributed equally between the two side gears. As a result, the pinion gears revolve with the pinion mate shaft but do not rotate around it (Fig. 1).
When turning corners, the outside wheel must travel a greater distance than the inside wheel to complete a turn. The difference must be compensated for to prevent the tires from scuffing and skidding through turns. To accomplish this, the differential allows the axle shafts to turn at unequal speeds (Fig. 2). In this instance, the input torque applied to the pinion gears is not divided equally. The pinion gears now rotate around the pinion mate shaft in opposite directions. This allows the side gear and axle shaft attached to the outside wheel to rotate at a faster speed.