Fabco SDA-2300, Service Manual, Page: 6 / 41

1.0 INTRODUCTION
1.1 GENERAL DESCRIPTION
The Fabco Steerable Drive Axle consists of four major
assemblies; the axle housing, two steerable drive ends,
and a differential carrier. A steering tie rod links the right
and left steerable ends, and steering input is delivered via
a steering arm. The steering arm is usually located on the
left steerable end, although right hand or even dual
steering arms are available.
1.2 OPERATION
Driving forces are put into the axle at the pinion yoke on
the differential carrier; they pass through the differential
to the inner axle shafts and on to the universal joints. The
yoke shafts get their power from the U-joints and transfer
it by means of splines to the drive flanges, which are
bolted to the wheel hubs, thus rotating the wheels.
When steered, the outer section of each steerable drive
end rotates about the kingpin centerline. The U-joint, cen-
tered on the kingpin centerline, allows power to be trans-
mitted throughout the possible range of steering inputs.
The axle is equipped with S-cam air brakes and automatic
slack adjusters.
1.3 OPERATING INSTRUCTIONS
In conditions where the vehicle's rear wheels might spin,
such as sand, loose dirt, mud, snow, ice, or ascending
grades, the front drive axle can be shifted into operation
for improved traction. Engagement can be made at any
vehicle speed, provided that the rear wheels are not spin-
ning. Engagement is best accomplished when the engine
is pulling lightly.
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