Differential bearing preload
Differential bearings must be mounted with a preload of 0.50 mm, which is ensured by selecting the thickness of the adjusting rings «Si» And «S2» (see diagram), which simultaneously determine the side clearance in the meshing of the main gear gears.
Measuring the axial movement of the differential when adjusting the differential bearing preload
Remove the differential output shaft seal using a lever.
Press out the outer races of the tapered roller bearings using a Kukko 21/7 internal gear puller and a support mandrel.
Remove the differential bearing adjusting rings.
Press the outer races of the bearings without adjusting rings to the stop using a mandrel. It is best to use a set of mandrels 30-505 and 30-20 to press the outer race of the bearing from the side of the driven gear and a set of mandrels VW 295 and VW 511 to press the outer race of the bearing from the opposite side.
Install the differential in the clutch housing without the speedometer drive gear. The driven gear must be on the left side opposite the differential bearing cap.
Replace the differential bearing cover and tighten the bolts of its fastening crosswise to a torque of 2.5 kgf·m. The lid must be facing up.
Install the support mandrel VW 385/17 on the differential box (see diagram).
Install the indicator stand VW 387 and fix the indicator with a 30 mm extension on it.
Install the indicator leg on the support mandrel with a preload of 1 mm, and fix the indicator in this position by setting its arrow to zero.
Raise and lower the differential and read the differential axial movement on the indicator. which, for example, is equal to 1.42 mm.
Warning. To prevent the bearings from self-aligning, do not turn the differential when measuring its axial movement. Otherwise, the indicator readings will be incorrect.
According to the formula So6=A+B calculate the total thickness of shims S1 and S2, where:
So6 - the total thickness of the differential bearing adjusting rings;
A - the value of the axial movement of the differential;
B is the value of the differential preload.
Example. The indicator reading when the indicator is moved is 1.42 mm, the differential bearing preload is 0.50 mm.
So6 = 1.42 + 0.50 - 1.92 mm
Install ring thickness «S06», equal to 1.92 mm, under the outer ring of the tapered roller bearing in the cover instead of the adjusting ring «S2».
Tighten the differential cover bolts.
Lubricate the differential bearings with gearbox oil.
Measure the moment of resistance to rotation of the differential with a dynamometer. It must be at least 250 Ncm for new bearings and at least 30 Ncm for worn-in bearings.
Measuring the moment of resistance to rotation of differential bearings
Adjustment of the side clearance in the gearing of the final drive gears
Install the secondary shaft, press in the outer pegs of the bearings with shims «S3» And «S4»
Install the differential with a washer pressed into the differential bearing cap «So6» instead of adjusting ring «S2».
Rotate the differential in both directions to self-align the bearings.
Install an indicator to measure the backlash in the final drive gear engagement with the differential rotating and the output shaft locked. The clearance must be measured at a diameter of 79 mm from the axis of the differential (nominal clearance should be within 0.10-0.20 mm).
Turn the driven gear all the way and set the indicator to the zero position. Rotate the driven gear all the way back and measure the backlash between the teeth of the drive and driven gears. Record the indicator readings.
Repeat the above operation three times, each time turning the driven gear 90°and unlocking the output shaft.
Warning. If the values obtained during measurement differ from one another by more than 0.06 mm, then the driven gear or the main pair are not installed correctly. Check the correct assembly and, if necessary, replace the main pair.
Calculate the average backlash between the teeth of the drive and driven gears.
Example. Suppose the value of the side clearance at the first measurement is 0.84 mm, at the second - 0.85 mm, at the third - 0.84 mm, at the fourth - 0.83 mm, i.e. the front gap is (0,84+0,85+0,84+0,83):4=0.84 mm. Calculate the thickness of the adjusting ring «S2» but the formula S2=So6-A+B. Where:
S2 - the thickness of the adjusting ring installed under the outer ring of the differential bearing from the side opposite to the ring gear of the driven gear;
So6 - total thickness of shims «S1» And «S2»;
A is the value of the average lateral clearance between the teeth of the driving and driven hysters;
B - estimated thickness of the ring «S2» (constant), equal to 0.15 mm.
Example. In our example «So6» equal to 1.92 mm, «A» - 0.84 mm, «IN» - 0.15 mm.
S2 = 1.92 - 0.84 + 0.15 = 1.23 mm
Calculate the thickness of the adjusting ring «Si» under the outer ring of the differential bearing, mounted on the side of the ring gear of the driven gear, according to the formula S1=So6-S2.
Example. In our example «So6» equals 1.92 mm. «S2» - 1.23 mm.
S1 = 1.92 - 1.23 = 0.69 mm
Since the tolerance limits for the thickness of the shims are known, in all cases the calculated thickness of the shims can be adjusted with high accuracy.
Take measurements of the thickness of the adjusting rings around the circumference with a micrometer at several points. In addition, make sure that there are no burrs or other defects on the surface of the rings. Install only good quality shims of the correct thickness «S1» And «S2». Carry out a control measurement of the side clearance between the teeth of the driving and driven gears at four points along the circumference. The clearance should be within 0.10-0.20 mm.
Warning» The measurement results should not differ from each other by more than 0.65 mm.
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