The cardan transmission of a car consists of four cardan shafts: the main shaft between the gearbox and the transfer case, the middle axle drive between the transfer case and the middle axle gearbox, the rear axle drive between the middle and rear axle gearboxes, and the front axle drive between the transfer case and the front gearbox bridge.

ZIL-131 cardan shaft layout

The design of all cardan shafts is the same (Fig. 2); the driveshaft of the middle axle drive is larger than all the others.

Each cardan shaft consists of a thin-walled tube, to one end of which a fixed yoke is welded, and to the other end a splined bushing 9 connected to a sliding yoke.

ZIL-131 rear axle cardan shaft

All eight joints of the cardan drive are identical in design and each consist of a fixed or sliding fork, a fork flange 18 and a cross 1 installed in the lugs of the forks on needle bearings 16.

The hinge bearings are lubricated through the oiler 2, screwed into the body of the cross. Grease is supplied to the bearings through axial channels.

To retain the lubricant, rubber seals are mounted in the bearing race.

There is a safety valve 19 in the center of the cross, through which, when the cross is filled with oil, excess oil escapes, thereby protecting the oil seals from damage as a result of increased oil pressure.

The cardan shafts have a sealed spline connection.

Grease in the inner cavity of the bushing is kept from flowing out by a plug 7 rolled into the splined bushing 9, as well as rubber 11 and felt 13 rings.

Both rings in combination with a 4 spline protection sleeve prevent contamination of the spline. The protective sleeve is fixed on the shaft with two strands of cotter pin.

The cardan shafts are dynamically balanced. Balancing of all cardan shafts, except for the main one, and the rear axle shaft is carried out by welding balancing plates 6 at the ends of the pipe.

Balancing the driveshaft of the rear axle and the main driveshaft on the side of the blind fork is achieved by welding the balancing plates on the pipe, and on the side of the sliding fork, by screwing the balancing plates to the ends of the fork lugs.

There is no protective clutch on the main propeller shaft connecting the gearbox to the transfer case.

Care of cardan shafts

The following is required when operating the vehicle:

  • 1. Systematically check the fastening of the cardan shaft flanges. All mounting bolts must be fully tightened.
  • 2. When loosening the bolts securing the base plates of the bearings of the cross, tighten them (the tightening torque should be equal to 1.4-1.7 kgm).

If there is a significant radial and end clearance in the bearings of the crosses, disassemble the hinges and, if necessary, replace the bearings or crosses.

  • 3. Check spline clearance periodically. With a large gap due to wear of the splines, the shaft must be replaced.
  • 4. When disassembling the rear axle driveshaft hinge and the main driveshaft, mark the balancing plates screwed to the ends of the lugs of the fork in order to put them in their original place during assembly.

After assembling the cardan shaft, it is necessary that the arrows stamped on the tubular shaft and the sliding fork are located one against the other; cross lubricators should be turned towards the shaft (for ease of lubrication), and not towards the flange; the crosses must turn in the bearings without jamming.

The bolts of the needle bearing support plates must be tightened and locked by bending one lug of the lock plate to the face of the head of each bolt.

After replacing individual parts, the cardan shaft must be dynamically balanced by welding plates 6 or installing removable plates under the heads of the bolts for fastening the base plates of the bearings of the cross, for all shafts, except for the middle axle shaft, the allowable unbalance is not more than 70 Gcm, and for the middle axle shaft 100 gsm.

The total thickness of removable balancing plates should not exceed 3 mm.

  • 5. Strictly observe the timing of lubrication of the driveline according to the lubrication chart.

Lubricate needle bearings 16 (Fig. 2) through the oiler in the cross until the oil starts to exit through the safety valve.

Before lubricating the crosses of the cardan shafts, it is necessary to carefully clean the grease fittings from dirt.

When adding lubricant, it is squeezed out of the safety valve after five to eight swings of the lever-plunger syringe.

If there is no lubrication in the hinge, the its infusion from the safety valve occurs after 45-50 swings of the lever-plunger syringe.

For lubrication, the spline connections must be disassembled, unscrew the plug 8; wash the splines of the sliding fork and the inner cavity of the splined bushing, put fresh grease into this cavity and reassemble the shaft.

After assembling the shaft, put plug 8 back in place.

When lubricating a splined joint, you must use the specific amount of grease indicated on the grease chart.

It is impossible to add grease through plug 8 in the spline connection without disassembling the cardan shaft.

When assembling the spline connection, it is necessary to ensure that the split washers 14 of the felt ring 13 are installed with a cut in different directions.


During operation, it may be necessary to adjust the full opening of the carburetor throttle valve and the position of the pedal

- Cause of malfunction Elimination method The clutch does not disengage completely (the clutch “drives”):