REAR END AND AXLES

The rear end suspension allows the rear wheels to move up and over bumps and down and out of road depressions. The rear axle powers the rear wheels, unless, of course, the car has front wheel drive. The rear end consists of a differential assembly, a differential housing, two axles and axle housings, two coil or leaf springs, control arms, a sway bar, and shock absorbers. There are two general types of rear suspension systems used on cars today, coil spring and leaf spring.
Coil springs are made from a spring steel rod heated and shaped into a coil. This rod is then tempered to the proper tension for flexibility and strength. On cars equipped with coil springs, other cornponents;control arms and bushings, a sway bar, a track bar, and shock absorbers;hold the rear end housing in place.

The control arms are located between the rear axle housing and the front of the car. They permit upward and downward movement of the rear axle housing and prevent side or backward and/or forward movement. The control arm bushings prevent metal-to-metal contact between the arm and the frame and the rear axle housing. They act as a bearing surface and also absorb road shock.

The sway bar, also known as the track or stabilizer bar, is connected on one end to the right or left side of the rear axle housing, and on the other to the frame. This bar keeps the body of the car from swaying from side-to-side.

Rear leaf springs may be multi- or single-leaf. Multi-leaf springs are composed of a number of graduated lengths of flat spring steel plates placed one on top of the other and secured with a center bolt. Some are equipped with side clips to prevent the individual leaves from shifting. Spring manufacturers may use inserts made of various materials, such as rubber pads, to allow for slippage between the leaves and to act as a lubricant.

The longest leaf, the main leaf, is rolled on both ends to form spring eyes through which the spring is mounted on the frame. The front end eye of the spring is attached to the frame with bushings and a bolt assembly. The rear end eye is attached with a shackle assembly allowing the spring to flex and change length when the rear wheels move up and down. The center of the spring is mounted on the rear axle housing with two U bolts.

The shock absorbers are mounted to the rear axle housing on one end and to the frame on the other. They restrain spring oscillation. Full details on how shock absorbers work were given in the previous chapter. The two rear axles are splined into the differential assembly and held in place with either a flange cap bolted to the outside ends of the axle housing, where the brake backing plate is also mounted, or with a C-type axle lock inside the differential assembly. The rear axle supports the weight of the rear of the car, through the rear axle bearing, and delivers turning power to the rear wheels. The differential assembly was described in Chapter 1.
In this chapter you will learn how to remove and replace the rear shock absorbers, the rear coil springs, the rear axles and bearings, and the rear axle seals.

Collapsed springs

Coil springs are mounted be-tween the frame and the axle housing. Rubber insulators be-tween a spring and its contact point prevent metal-to-metal contact. Signs of rubbing be-tween individual coils indicate the coils have made contact, and suggest a collapsed spring. An-other indication of a weak or collapsed coil spring is a sagging, tail-dragging ride. Still another is bottoming, a loud, heavy, thumping sound when going over bumps or road dips with a normal passenger load.

Single-leaf and double-leaf springs

The single-leaf spring is a one-piece semielliptical spring which is long and wide. It is used lighter cars and is mounted and functions in the same way as the multi-leaf spring.