Adjusting the distance between the end of the drive gear and the differential axle (VW Passat B2)

Principle of regulation

The distance between the differential axis and the end of the drive gear determines the location of the contact patch in the engagement of the main gear gears. When installing the secondary shaft in the gearbox, this distance affects the degree of wear and noise of the main gear gears. Therefore, it must be adjusted with particular care using a special tool.

The initial value for adjustment is the calculated value of the distance between the differential axis and the end face of the drive gear (dimension "Ro", see diagram), adjusted by the correction "r", determined during the manufacture of the drive gear. The adjustment consists of placing the adjusting ring S3 of the required thickness under the outer ring of the secondary shaft rear bearing to shift the drive gear in the gearbox housing.

Determining the value of the correction "r"

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Note: This measurement is taken if the driven gear of the main transmission does not have the correction marking "r" in hundredths of a millimeter from the nominal position of the driving gear, and also if parts/directly affecting the position of the driving gear of the main transmission have been replaced (secondary shaft rear double-row tapered roller bearing, gearbox housing or rear cover, 1st gear pinion bearing).

Remove the rear gearbox cover.

Install a special adjusting washer VW 381/11 and secure it strictly at a right angle relative to the secondary shaft, tightening two M8x50 bolts by hand.

Tighten the bolts to 2 Nm using a torque wrench.

The pinion gear, after tightening the bolts, assumes the position it occupied when the rear cover of the gearbox was installed. This operation must be carried out very carefully every time the distance between the end of the pinion gear and the differential axle is adjusted.

Remove the differential.

Install the VW 385 measuring mandrel into the clutch housing (calibrated to a preload of 2 mm) to "zero" using the VW 385-30 indicator.

Determine the calculated value of the dimension "r", which is the deviation from the dimension "Ro".

When replacing parts, select the thickness of the adjusting ring to achieve maximum possible accuracy in maintaining the obtained size "r".

Selecting the secondary shaft rear bearing adjusting ring

If the final drive is to be used again, press the outer race of the rear bearing together with the old adjusting ring into the gearbox housing. If parts have been replaced, install the outer race of the bearing without the adjusting ring.


Install the secondary shaft and press on the second inner race of the rear bearing.

Tighten the secondary shaft rear end nut to a torque of 10.0 kgf·m.

Install the special secondary shaft preload adjusting washer VW 381/11 as described in the previous paragraph.

Install the VW 385 measuring mandrel (calibrated with a preload of 2 mm) to "zero" using the VW 385-30 indicator and measure the value of "r" and compare it with the calculated value of "r" if the main gear was replaced, or with the value marked on the driven gear when the main gear was replaced. If the obtained value of "r" is less than the calculated value, then the adjusting ring S3 of greater thickness should be installed, and vice versa. The difference between the obtained and calculated values of "r" shows how much the thickness of the adjusting ring S3 should be reduced or increased.

Remove the measuring instrument kit and install the selected adjusting ring S3 under the outer ring of the secondary shaft rear bearing.

Check that the adjustment is correct.

Selecting the differential bearing adjusting ring

The differential bearings must be installed with a preload of 0.40 mm.

Remove the sealing rings, press the outer rings of the differential bearings out of the clutch housing and remove the adjusting rings.

Press in the outer ring of the tapered roller bearing from the side opposite the teeth of the driven gear of the main transmission, with the installation ring "A" (see diagram) with a thickness of 1.20 mm.

Press in the outer ring of the differential bearing from the side of the driven gear teeth without the adjusting ring.

Install the differential with the pressed inner bearing races without the speedometer drive pinion and install the differential cover.

Install the differential so that its axis is in the vertical plane (see diagram).

Install the indicator support frame onto the differential case.

Fix the indicator with a scale of 0-3 mm using a special device. Install the indicator leg on the support mandrel with a preliminary tension of 1 mm. Fix the indicator in this position and set it to "zero".

By moving the differential up and down, using VW 521/4 and VW 521/8 bushings if necessary (see diagram), determine the axial displacement "B" of the differential using the indicator and calculate the thickness "S" of the differential bearing adjusting ring using the formula:

S=A+B+C,

where:
S — thickness of the adjusting ring;
A - thickness of the mounting ring, equal to 1.20 mm;
B is the value of the differential axial displacement;
C is the value of the differential bearing preload, equal to 0.40 mm.

Install adjusting rings of the required thickness under the outer ring of one of the differential bearings and check the lateral clearance in the engagement of the main gear gears. If new bearings are installed, check the torque of resistance to turning of the differential, which should be equal to 250 N·cm.

Adjusting the lateral clearance in the engagement of the main transmission gears

This adjustment is necessary when replacing the main gear of the gearbox housing, differential box and bearings, as well as when adjusting the distance between the end of the drive gear and the differential axis.

Install the secondary shaft and differential.

Turn the differential several times to adjust the bearings.

Install devices for measuring the lateral clearance between the teeth of the driving and driven gears when the differential is rotating and when the secondary shaft is stationary; the measurement is taken along the diameter at a distance of 71 mm from the differential axis. The lateral clearance between the teeth of the driving and driven gears should be within 0.10-0.20 mm.

If the clearance is not within the specified limits, move the adjusting rings from one side of the differential to the other until the normal clearance is obtained.