Measuring gear backlash between drive pinion and crown wheel and correcting if necessary - AR35.31-P-0550-25D

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Test values of rear axle center assembly gear set

Number	Designation		Model 124	Model 129	Model 140
BE35.31-P-1002-03A	Gear backlash between drive pinion and ring gear	mm	0.08 - 0.14	0.08 - 0.14	0.08 - 0.14

Test values of rear axle center assembly gear set

Number	Designation		Model 210
BE35.31-P-1002-03A	Gear backlash between drive pinion and ring gear	mm	0.08 - 0.14

Fig 1: Identifying Gear Backlash Measuring Device (201 589 03 21 00)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Install gear backlash measuring device (037) with dial gauge in the left-hand bore of the differential housing and clamp securely.
Set dial gauge on "0" with 3 mm preload.
Hold the drive pinion securely at the joint flange and move the handle (arrow) of the gauge stand alternately to the left and right, reading off the gear backlash.
Carry out the measurement four times, always turning the ring gear through a further approx. 90° each time.
Remove gear backlash measuring device.

The adjustment of the tapered roller bearings and the gear set is in order if the spread dimension (enlargement) of the rear axle housing and the gear backlash are within the range of the specified values. If these values are not achieved, the adjustment must be repeated with suitably thicker or thinner shims.

Fig 2: Identifying Gear Backlash Measuring Device

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

1st. example

Measurement: Gear backlash is correct, but the expanded dimension of the rear axle housing is too small.

Correction: Mount shims which are thinner by the same amount on both side bearing covers, the gear backlash may change slightly in the process!

2nd. example

Measurement: Expanded dimension is correct, but the gear backlash is too large.

Correction: A shim which is thicker by the missing amount is to be installed on the left assembly side.

A shim which is thinner by the missing amount is to be installed on the right assembly side (ring gear side).

Proceed in the reverse order if the gear backlash is too small.