Setting crownwheel and pinion backlash and preloading differential bearings using adjusting nuts

(Figs 7.6 and 7.7) Locate the differential bearing caps on their cones and position the differential assembly in the final drive housing. Refit the bearing caps with the mating marks aligned and replace the bolts so that they just nip the caps in position. Screw in the adjusting nuts whilst rotating the crownwheel until there is just a slight backlash. Bolt the spread gauge to the centre bolt hole of the bearing cap and fit an inverted bearing cap lock tab to the other cap (Fig. 7.7). Ensure that the dial gauge spindle rests against the lock tab and set the gauge to zero. Mount the backlash gauge magnetic base stand on the final drive housing flange so that the dial spindle rests against a tooth at right angles to it and zero the gauge (Fig. 7.6). Screw in the adjusting nuts until a backlash of 0.025 to 0.05 mm is indicated when rocking the crownwheel. Swing the backlash gauge out of position.

Screw in the adjusting nut on the differential side whilst rotating the crownwheel until a constant cap spread (preload) of 0.20-0.25 mm is indicated for new bearings, or 0.10-0.125 mm when re-using the original bearings.

Swing the backlash gauge back into position and zero the gauge. Hold the pinion and rock the crownwheel. The backlash should now be 0.20-0.25 mm for new bearings or 0.10-0.125 mm with the original bearings.

If the backlash is outside these limits, adjust the position of the crownwheel relative to the pinion by slackening the adjusting nut on one side and tightening the nut on the other side so that the cap spread remains unaltered. The final tightening must always be made to the nut on the crownwheel side.

Refit the lock tabs left and right hand and torque down the cap bolts; a typical value for a car axle is 60-70 Nm.

Pitch line The halfway point on the tooth profile between the face and the flank is called the pitch line.

Tooth root The bottom of the tooth profile is known as the tooth root.

Tooth face The upper half position of the tooth profile between the pitch line and the tooth tip is called the tooth face.

Tooth flank The lower half position of the tooth profile between the pitch line and the tooth root is called the tooth flank.

Tooth heel The outer large half portion of the crownwheel tooth length is known as the heel.

Tooth toe The inner half portion of the crownwheel tooth length is known as the toe.

Drive side of crownwheel tooth This is the convex side of each crownwheel tooth wheel which receives the contact pressure from the pinion teeth when the engine drives the vehicle forward.

Coast side of crownwheel tooth This is the concave side of each crownwheel tooth which contacts the

Backlash Engineering
Fig. 7.6 Checking crownwheel and pinion backlash
Fig. 7.7 Setting differential cage bearing preload using adjusting nuts

pinion teeth when the transmission overruns the engine or the vehicle is being reversed.

Crownwheel and pinion backlash The free clearance between meshing teeth is known as backlash.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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Responses

  • Addison
    What is backlash setting crown wheel?
    2 years ago
  • Ali
    What is mean by crwon wheel pinion prelaoding?
    2 years ago
  • kedija
    Why differential crown wheel in left?
    2 years ago

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