Steering System Updates

STEERING SYSTEM

Steering Column

The new steering column has the following features:

^ Tilt and reach adjustment

^ Entry/exit feature

^ Automatic tilt away (powered version)

^ Infinitely variable positions (within a range)

^ Improved ergonomic key position

^ Multi-position column lock.

Depending upon model specification, tilt and reach adjustment is performed by electrical or manual operation. Powered variants may be either automatically or manually adjusted. All types have the entry/exit feature.
The column uses carry-over mountings, i.e. upper swing link (Vee bracket) and lower body-in-white fixings. The column covers are new with a common upper section. The lower sections differ for power or manual column adjustment variants. The upper column universal joint is new.

Operating Description

Powered Steering Column








Two independent motor/gearbox assemblies provide infinite adjustments for tilt and reach within approximate ranges of 13 and 35mm respectively. Adjustments may be automatically made in conjunction with the seat memory facility or manually using the steering adjustment switch. When the steering switch is moved to OFF, the automatic exit/entry feature is disabled.

Manual Steering Column





Tilt variations are stepped at approximately 3 intervals. Six positions are available with the uppermost position being unlatched. The cable operated reach adjustment is infinite within a range of 35mm. The desired position is maintained by a rack and wedge latch mechanism.

WARNING: COLUMN TRAVEL SHOULD BE MANUALLY RESTRAINED TO CHECK UPWARD SPRING ASSISTANCE. RESTRAINT IS ESPECIALLY IMPORTANT IF THE STEERING WHEEL HAS BEEN REMOVED FOR MAINTENANCE REASONS.


Variable Assist Power Steering System (Servotronic)

Features

The 'Servotronic' system provides full power assist to reduce steering effort during parking and low speed maneuvers and progressively reduces power assistance as the vehicle speed rises. This feature enhances steering 'feel' at highway speeds.

System Components

The variable assist steering system is made up of the following components:

^ An engine driven rotary vane pump,
belt drive on V12 engines, direct drive from the timing gear on six cylinder engines. The pump has a falling flow characteristic (as pump speed increases, fluid flow decreases) and an integral pressure release valve.


^ A remote fluid reservoir,
with integral 'return' line filter.


^ The steering rack,





incorporating a speed sensitive transducer.


^ A steering control module (SCM),





located on the left 'A' post.

^ A fluid cooler with associated pipework. The fluid cooler, situated in the radiator pack, is unchanged from the previous model year condition.


System Description





Steering System Schematic Diagram

The Servotranic system uses a rotary valve within the pinion housing which is fitted with a hydraulic reaction piston (HRP). Inputs to the HRP are:

^ Differential pressure on the piston rack,
proportional to vehicle cornering force

^ The position of the transducer valve,
controlled by the steering control module from road speed data.