General information about the transmission line (BMW 5 Series E28)

General information

This Chapter describes the components that transmit rotation from the gearbox to the drive wheels of the vehicle. These components include the propeller shaft, final drive assembly, and rear axle drive shafts.

Cardan shaft

Engine power is transmitted from the transmission to the rear axle via a two-section propeller shaft connected behind the central bearing by a so-called "sliding coupling", a splined sliding connection. The sliding coupling allows slight longitudinal movements of the propeller shaft. The front end of the propeller shaft is attached to the transmission flange by means of an elastic rubber coupling.

This coupling, sometimes called a "Guibo" or "flexible disk", protects the driveshaft and differential from jerking when the engine rotates. On some models, a vibration damper is installed between the output flange of the transmission and the flexible coupling. The middle of the driveshaft is supported by a central bearing mounted on a rubber cushion to dampen shaft vibration.

The bearing housing is bolted to the car body. The front end of the driveshaft is aligned with the transmission by means of a centering guide machined into the driveshaft; the centering guide connects to the centering pin on the transmission flange. Universal joints are located at the center bearing and at the rear end of the driveshaft to compensate for the movement of the transmission and differential on their supports, as well as any deflection of the chassis.

Differential/Final Drive Assembly

The differential assembly, located at the rear of the vehicle, includes the pinion gear, ring gear (driven gear), differential and output flanges. The pinion gear that turns the ring gear is sometimes called the differential input shaft. It is connected to the driveshaft via a flange. The differential bolts to the driven gear and turns the rear wheels through a pair of output flanges that are attached to the drive shafts via constant velocity joints (CV joints). The differential allows the wheels to rotate at different speeds during cornering (the outer wheel should move slightly faster than the inner wheel due to the difference in turning radii). The differential assembly is bolted to the rear axle carrier and to the body using elastic rubber bushings.



Major repair of differential assembly components (pinion, ring gear and differential) requires a lot of special tools and equipment, as well as considerable experience, and therefore is best left to the specialists at a BMW dealer service department or auto repair shop.

Drive shafts and CV joints

Drive shafts transmit rotation from the differential output flanges to the rear wheels of the vehicle. Drive shafts are equipped with constant velocity joints (CV joints) at both ends.

The function of a CV joint is basically the same as a standard universal joint, but a CV joint can accommodate greater drive shaft deflection angles than a universal joint. CV joints allow the drive shafts to transmit rotation to the rear wheels by moving up and down with the rear suspension, even when the differential assembly, drive shafts, and wheels are out of balance.

The inner CV joints on all models are bolted to the differential flanges. The outer joints are identical to the inner ones. Each joint is filled with special grease and covered with a rubber protective cover. Regularly check the condition of the protective covers. Damage to the cover leads to contamination of the joint.

The joints on the vehicles covered in this manual are not repairable, but they can be removed and cleaned when the protective boots are replaced. Both inner and outer CV joints on all models are individually replaceable.

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