Steering (Description): Description and operation (page 2 of 2)

Tilt adjustment The column tilt adjuster lever mechanism is located on the LH side of the steering column and allows the upper column tube, nacelle and steering wheel assemblies to be tilted up or down a maximum of 7.5° or 47 mm (NAS vehicles have a smaller range of movement than the ROW vehicles).

The pawl of the mechanism is attached to the lower column and is allowed to pivot, a toothed quadrant is fixed to the upper column tube.

When the lever on the LH side of the steering column is raised the mechanism releases the pawl from the toothed quadrant, this allows the column to be moved. When the lever is released two return springs pull the pawl into engagement with the toothed quadrant.

Steering column lock (All except NAS) The steering column lock houses the ignition switch, ignition illumination light ring, key lock barrel and the alarm passive coil. The steering lock is attached to the upper column with two shear bolts. The bolts are tightened to a torque which shears off the heads of the bolts preventing easy removal of the steering lock.

The steering lock operates by a bolt, which emerges when the ignition key is turned to position 'O' and the ignition key removed. The bolt engages in a lock collar located on the upper shaft in the upper column tube. The lock collar is attached to the upper shaft by a 'wave form' interference ring. If a high torque is applied via the steering wheel with the lock engaged, the lock collar will slip on the upper shaft. This prevents damage to the steering lock, yet still prevents the vehicle from being driven.

Steering column lock (NAS only) The steering column lock houses the ignition switch, ignition illumination light ring, key lock barrel and the alarm passive coil. The steering lock is attached to the upper column with two shear bolts. The bolts are tightened to a torque which shears off the heads of the bolts preventing easy removal of the steering lock.

The steering column lock operates by a bolt, which emerges when the ignition key is turned to position 'O' and the ignition key removed. The bolt engages in a groove machined into the upper shaft in the column tube.

Steering wheel The steering wheel comprises a cast centre and wire frame onto which the soft polyurethane foam is moulded. The steering wheel is located on the upper column shaft by a spline and is secured with a nut. A remote radio control switch (if fitted) is located on the LH side of the steering wheel, a cruise control switch may be located on the RH side. Horn switches are located on each side of the centre of the steering wheel and protrude through the airbag module cover. Both switches are connected by wires to the rotary coupler connector.

Intermediate shaft One end of the intermediate shaft is attached to the steering column lower shaft by a splined universal joint and a bolt, the universal joint is part of a rubber coupling assembly. The rubber coupling assembly is covered by a heat shield and connects to the lower section of the intermediate shaft via a decouple joint. The rubber coupling reduces the shocks felt by the driver through the steering wheel. A second universal joint on the other end of the intermediate shaft is held in by a bolt. The universal joint is splined and engages with the splined rotor (input) shaft of the steering box.

The decouple joint consists of a metal plate that has open ended slots, the plate is bolted through the slots into the other half of the decouple joint. The top half of the decouple joint has a slot that accepts the lower section of the intermediate shaft. The slotted metal plate clamps the lower section of the intermediate shaft to the top section. An indicator clip is installed between the slotted metal plate and the top half of the decouple joint.

If the intermediate shaft is compressed in an accident, the slotted metal plate in the decouple joint will disengage if sufficient force is applied to the front end of the shaft. If the forces involved do not disengage the shaft, the red indicator clip located in the decouple joint will break off if the shaft moves. The intermediate shaft cannot be repaired and must be replaced as an assembly if accident damage occurs.