Suspension: Description and Operation
INTRODUCTION
This section describes the front and rear suspension Systems, and also covers diagnostic procedures.
FRONT SUSPENSION, DESCRIPTION & LAYOUT
The upper rear wishbone (1 Fig. 1) and the upper front wishbone (2 Fig. 1) are pivoted on the upper fulcrum bolt (3 Fig. 1), passing through the front cross beam assembly. They are also fitted via an upper ball joint assembly (4 Fig. 1) to a vertical link accommodating the stub axle (5 Fig.1), whereas the vertical link is fitted via a lower ball joint assembly (6 Fig.1) to the lower wishbone assembly.
The lower wishbone assembly comprises a lower rear wishbone arm (7 Fig.1), lower front wishbone arm (8 Fig.1), damper (9 Fig.1) (incorporating damper bush 10 Fig.1) and spring pan (11 Fig.1) supporting the road spring (12 Fig.1). The lower wishbone assembly is pivoted on the bushed lower fulcrum shaft (13 Fig.1) which also passes through the cross beam assembly.
Both independent front suspension assemblies are linked by a stabilizer bar (14 Fig.1) which is secured to the cross member using a fixing arrangement of mounting rubbers (15 Fig.1) clamps (16 Fig.1), nuts bolts, washers (17 Fig.1) and two link arm assemblies (18 Fig.1). Each link arm assembly is fitted to one end of the stabilizer bar and to one end of the lower front wishbone using a fixing arrangement of bolts washers and self locking nuts.
The degree of caster is adjustable via shims positioned on either side of the upper ball joint assembly but camber is not adjustable. The vertical link and the steering arm form a single forging. Cast iron hubs rotate on twin tapered roller bearings.
Front Suspension Updates
The springs, shock absorbers and stabilizer bar are retuned.
As a minor modification to the cross-beam, a clip location loop is added. Its purpose is to provide a means to secure the new power steering electrical link lead away from the steering pinion area.
As part of a refinement initiative, the two front Vee mounts that locate the front subframe to the body longitudinal members, are modified. The new Vee mounts alter the lateral and vertical static stiffness.
With the revised dynamic specification, the new Vee mounts: reduce rear seat cabin boom; improve road noise isolation; reduce road surface ridge harshness.
Additionally, the rear engine/transmission mounting is completely revised. The former twin spring design, attached to the body-in-white, is replaced by a rubber to metal mount. The mount is secured to a support bracket which bridges the two body underframe longitudinal members.
REAR SUSPENSIONS, DESCRIPTION & LAYOUT
The vehicle's rear suspension layout features a cast wishbone complete with integral lower spring pan (1 Fig.1) sup- porting the independently mounted damper (2 Fig.1) and road spring (3 Fig.1).
The lower wishbone arm is bolted to the hub carrier (4 Fig. 1) by means of a pivot bolt (5 Fig.1), allowing for toe-in adjustment. When the pivot bolt is seated correctly in the machined groove of wishbone arm, it has a small clearance at the sides but full clearance at the top and bottom.
Rotation of the bolt head, with eccentric constrained between the vertical faces, causes the bolt shank to be moved in the horizontal plane, thus displacing the hub carrier and effecting wheel alignment adjustment.
The snubber (6 Fig.1) positioned above the hub carrier, prevents this from touching the vehicle body.
The hub carrier/wishbone assembly, is pivoted on the wishbone fulcrum bolt (7 Fig.1) and is then secured by a nut and washer fixing arrangement to the pendulum assembly (8 Fig.1) and the wishbone tie assembly (9 Fig.1).
The differential strut (10 Fig.1) is fastened to the wishbone tie assembly and to a bracket, welded to the vehicle body.
All suspension loads, except the damper, are fed into a steel crossbeam (Fig. 2) which is isolated from the body by rubber bushes. This mounting method allows the necessary amount of compliance.
The supercharged vehicle (manual only) is equipped with a rear stabilizer bar (1 Fig. 1), a differential monostrut (2 Fig. 1) instead of two single struts, a modified wishbone tie (3 Fig. 1) and two stabilizer bar drop links (4 Fig. 1) which are seated on the lower wishbone cast bosses.
The drop links attach the stabilizer bar to the wishbone. In addition the stabilizer bar is secured to the wishbone tie by two mounting rubber assemblies (5 Fig.1).
The supercharged automatic & XJ Sports versions, are fitted with subframes having stiffer bushes, two single struts and a rear stabilizer bar.
Rear Suspension Updates
The components supplied below apply to some, but not all, vehicle specifications.
The springs and shock absorbers are retuned.
Differential Strut
A redesigned differential strut is introduced on XJR (manual gearbox supercharged) vehicles. The former two differential struts are replaced by a single monostrut. The monostrut provides increased stiffness and reduces the possibility of axle tramp.
Wishbone Tie
The wishbone tie is modified to accommodate either the 'supercharged' differential monostrut or the two standard differential struts.
Stabilizer Bar
The rear stabilizer bar is a bayonet fit into the stabilizer bar drop links. Additionally, the stabilizer bar has two shoulders that locate on the mounting bushes to prevent lateral movement.
Stabiliser Bar Drop Link
The cast iron rear wishbone is modified to include lugs through which the two new stabilizer bar drop links are fitted. The drop links attach the stabilizer bar to the wishbone and allow movement as the suspension travels up and down. Each threaded drop link has two isolating rubbers and is secured to the lug with a nut and washer.