Chapter 5 Front Suspension Systems 97
U-joint
Tie rod tube
Steering damper
Steering arm
Tie rod end
Hub
Disc
brake
Differential
Figure 5-27. A solid driving front axle used on a four-wheel
drive vehicle. (Moog)
Since the operation of the four-wheel drive places
many forward and backward stresses on the suspension
components, other support is needed. Most solid axles
have control arms or strut rods to keep the axle in place.
Twin I-Beam Axle Front Suspensions
Until recently, twin I-beam axle front suspensions
were used on many Ford trucks. This type of front
suspension actually uses two I-beams, one at each wheel.
The inner portion of each I-beam is attached to the frame
on the opposite side of the wheel that it serves. The I-beam
pivots on bushings similar to those used on the control
arms of a conventional suspension. The outer end of the
I-beam is attached to the steering knuckle, usually through
ball joints. Some older systems may have kingpins. The
twin I-beam design results in a strong axle with better han-
dling characteristics than a single solid axle.
The exact design of the twin I-beam front axle varies
between two- and four-wheel drive vehicles. The differ-
ences between each type are covered below.
Non-Driving Twin I-Beam Axle
The typical non-driving twin I-beam axle is shown in
Figure 5-30. Each I-beam is connected at the frame through
a large single bushing. A coil spring is installed between
the top of the I-beam and the frame, and is usually clamped
in place. Twin I-beam assemblies use strut rod assemblies,
usually called radius arms, to eliminate forward and back-
ward movement of the I-beam. A stabilizer bar assembly is
also used to reduce body lean on turns.
Driving Twin I-Beam Axle
A driving twin I-beam axle resembles a non-driving
twin I-beam assembly. The main difference is that the final
drive assembly (ring and pinion, differential gears) is
installed in the left I-beam, Figure 5-31. Power from the
final drive assembly operates axles installed in each I-beam
assembly. U-joints at each steering knuckle transfer power
from the drive axles to the stub axles. The steering
knuckles are similar to those used on solid drive axles.
Locking hubs are also used with some older four-wheel
drive twin I-beam vehicles.
Washer
Body assembly
Cover assembly
Clutch OFF
Snap ring
Knob
Hub
Bush
Axle shaft
Snap ring
“FREE” position “LOCK” position
Clutch ON
Figure 5-28. Cutaway of a four-wheel drive manual locking hub. Note the difference between “free” and “lock” positions. (Suzuki)