Steering Gear: Notes
| ITEM | DESCRIPTION |
|---|---|
| 1 | Input shaft |
| 2 | Valve unit |
| 3 | Servotronic valve |
| 4 | Pressure/Return pipes |
| 5 | Tie-rod |
| 6 | Locknut |
| 7 | Tie-rod end |
| 8 | Locknut |
| 9 | Steering gear boots |
| 10 | Mounting bolts and washers |
| 11 | Pinion housing |
| 12 | Pressure/Return connection from/to pump |
The steering gear is located at the rear of the engine and attached to the front sub-frame. The gear is secured to the sub-frame with three bolts and washers which screw into threaded tubes which are integral with the subframe.
The steering gear comprises an aluminum, cast, valve housing which contains the hydraulic valve unit and Servotronic valve. The mechanical steering rack and the hydraulic actuator are located in a steel cylinder which is attached to the cast valve housing.
The steering gear uses a rack with an integrated piston which is guided on plain bearings within the cylinder and the valve housing. The pinion, which is attached to the valve unit, runs in bearings and meshes with the rack teeth. The rack is pressed against the pinion by a spring loaded yoke which ensures that the teeth mesh with the minimum of play. The pinion is connected to the valve unit via a torsion bar. The rotary motion of the steering wheel is converted into linear movement of the rack by the rack and pinion mechanism and is initiated by the valve unit. This movement is transferred into movement of the road wheels by adjustable tie-rods.
The teeth angles at the center of the rack vary from those at the end sections. It is this variation in teeth angles which provides the variable ratio.
The piston of the hydraulic actuator is located on the rack bar. Each side of the piston is connected to fluid pressure or fluid return via external metal pipes which are connected to the valve unit.
Each end of the rack bar has a threaded hole which provides for the fitment of the tie-rod. The external ends of the gear are sealed with boots which prevent the ingress of dirt and moisture. The tie-rod has a long threaded area which allows for the fitment of the tie-rod end. The thread allows for the adjustment of the steering toe. When the correct toe setting is achieved, a locknut is tightened against the tie-rod end preventing inadvertent movement.
The gear has a central hole machined along most of its length. The hole allows the air in the boots to be balanced when the steering is turned. The boots are serviceable items and are retained on the gear housing and the tie-rod with clips.