Detailed technical specifications (BMW 3 Series E21)

Cardan transmission

The cardan transmission consists of two tubular shafts with an intermediate support attached to the bottom of the body, mounted on a ball bearing. The front cardan shaft is attached to the flange of the secondary shaft of the gearbox by means of a ring (on cars with manual transmission) or segmental (on cars with automatic transmission) elastic coupling.

Front propeller shaft

Shaft length "a" (see picture), mm:

• cars with 4-cylinder engines:
• with manual transmission ("A" in the figure): 711.3;
• with automatic transmission ("B" in the picture): 582.9;
• cars with 6-cylinder engines:
• with manual transmission: 636.5;
• with automatic transmission: 510.5.

Rear propeller shaft

Shaft length "b" (for all models), mm: 916.5.

The design of the rear propeller shaft on vehicles with 4- and 5-speed gearboxes is different.

The greatest permissible imbalance of the rear propeller shaft when measured at its center, gf cm:

• at a crankshaft speed of 3000 rpm for vehicles with 4-cylinder engines: 10;
• at a crankshaft speed of 3250 rpm for vehicles with 6-cylinder engines: 10.

Preload of intermediate support (towards the front of the car), mm: 2.

Rear axle

The rear axle is sprung, with a hypoid final drive. The final drive pinion rotates in tapered roller bearings. The final drive ratio is marked on the front left side of the final drive pinion.

Main gear brand: Klingelnberg or Gleason.

Heating temperature of the driven gear of the main transmission during installation,°C: 80-100.

The bearings are installed on the drive gear without preheating.

By special order, the vehicles were equipped with a rear axle with a limited-slip differential of the ZF brand, type Lok-O-Matic-DL-175.

Differential lock ratio, %: before April 1977: 40; since May 1977: 25 (marking S25).

The moment of resistance to rotation with a locked axle gear and the other axle gear driven into rotation, N·m: 30-50.

Disc thickness, mm:

• external: 1, 9; 2,0; 2,1;
• internal: 2.0.

Rear axle oil

Rear axle housing capacity, l: 0.95.

Oil used: SAE 90 hypoid oil.

Oil change frequency: after the first 1000 km of mileage, then every 30,000 km of mileage.

Rear wheel drive

The drive of each wheel consists of two constant velocity ball joints and a shaft.

Maximum angle of the wheel drive shaft, deg.: 18.



The gap between the side surface of the hinge and the flange when measured at a radius of 25 mm, mm: 0.08.

Maximum permissible displacement, mm:

• hinge:±6;
• semi-axles:±12.

The amount of grease placed in the hinge housing during assembly, g: 80 (for example. Shell Retinax AM).

Recommended brand of adhesive to use when installing the hinge protective cover: Bostik 475.

Recommended brand of sealant to use when installing the hinge cover: Curil K.

Tightening torques of main threaded connections, kgf·m

• Elastic coupling mounting bolt nut: on vehicles with manual transmission: 6.9-7.7; on cars with automatic transmission: 4.4–4.9.
• Nut of bolts fastening the flange of the cardan shaft to the flange of the gearbox: 6.9-7.7.
• Front propeller shaft fork mounting nut (M12x1.5): 9.7-10.7 (pre-apply a sealant such as Loctite 270 to the threaded end of the shaft).
• Nuts for the bolts securing the intermediate support crossmember to the body floor: 2.2–2.4.
• Nuts for bolts securing the rear axle housing to the bracket: 8.1—9.2.
• Nut of the bolt securing the rear axle housing to the bracket: 8.1—9.2.
• Nut of the bolt securing the rocker support to the rear axle housing: 8.1-9.2.
• Bolts for fastening the cover to the rear axle housing (M10): 4.4–4.9.
• Filler and inspection hole plug (M22x1.5): 5.1-6.1.
• Bolts for fastening the driven gear of the main transmission to the differential box: 8.7-10.2 (apply a thread sealant such as Loctite 270 to the threads first).
• Nuts for fastening the flange to the drive gear: not less than 15.3.

This article is based on information from the website «BMWman.ru»