Differential Assembly
Establish gear wheels of semiaxes with basic washers and satellites. Turn the planets and gears of the axle shafts so that the axis of rotation of the planets is aligned with the axis of rotation in the box, then insert the axis of the planets. Check the axial play of each axle gear: it should be no more than 0.10 mm. If the clearance is increased, which is a sign of excessive wear of the gears, replace the support washers of the gears of the axle shafts with others of greater thickness. If the specified clearance cannot be obtained even when installing washers of the greatest thickness, replace the gears with new ones.
Install the driven gear and, using mandrel A.70152, press the inner rings of the bearings onto the differential box. The mandrel is made of a pipe with an outer diameter of 43 mm and an inner diameter of 35.2 mm.
Installing and adjusting the drive gear
Having fixed the crankcase on the stand, press the outer rings of the front and rear bearings of the drive gear into the housings of the crankcase, using mandrels A.70185 for the front bearing and A.70171 for the rear (pic. 135).
On mandrel А.70184 (pic. 136), simulating the drive gear, install the inner ring of the rear bearing and insert it into the neck of the gearbox housing. Install the front bearing inner race, the drive gear flange and, turning the mandrel to properly install the bearings, tighten the nut (tightening torque 0.8—1.0 kgf·m). Fasten fixture 2 (A.95690) on the end of mandrel 1 and adjust the indicator having a division of 0.01 mm by zero by setting its leg on the same end of mandrel A.70184. Then move the indicator so that its leg rests on the seating surface of the differential case bearing. Turning the mandrel with the indicator left and right, set it to a position in which the indicator needle marks the minimum value of a1, and write it down. Then repeat this operation on the seating surface of the second bearing and determine the value of a2. After that, determine the thickness S of the drive gear adjusting ring:
S = a — b
where a= (A1+a2) /2 is the arithmetic mean distance from the ends of the mandrel to the necks of the differential bearings; b - deviation of the drive gear from the nominal position, mm.
The deviation value is marked on the drive gear in hundredths of a millimeter with a plus or minus sign. When determining the thickness of the adjusting ring, the sign of the value of b and its unit of measurement should be taken into account.
Example. Assume that the value of a, set using the indicator, is 2.91 mm (a is always positive), and on the drive gear after the serial number is the number -14. To obtain the value of b in millimeters, the indicated number should be multiplied by 0.01 mm, i.e. b \u003d -14 0.01 \u003d -0.14 mm.
Determine the thickness of the adjusting ring for the drive gear (mm):
S=a—b=2,91— (—0,14) =2,91+0,14=3,05.
In this case, it is necessary to install an adjusting ring with a thickness of 3.05 mm.
Put on the drive gear 29 (see fig. 128) adjusting ring 21 of the required thickness and press with mandrel A.70152 the inner ring of the rear bearing, removed from mandrel A.70184. Put on the spacer sleeve.
When overhauling the gearbox, a new spacer must be installed if the gearbox housing, final drive gears, and pinion bearings have been replaced. If the specified parts remain the same, the spacer sleeve can be reused.
Insert the drive gear into the gear housing and install the front bearing inner race, oil slinger, oil seal, drive gear flange and washer onto it. Screw a nut onto the end of the drive gear and, locking the flange of the drive gear, tighten it (tightening torque 12-26 kgf·m).
Tightening the pinion bearings
To limit the axial displacements of the drive gear under operating loads, it is very important to create a preload in its bearings within the specified limits. The preload is controlled by a dynamometer 02.7812.9501, which allows you to measure the moment of resistance to turning the gear. This torque determines the degree of tightening of the bearings. It should be 16-20 kgf cm for new bearings and 4-6 kgf cm for bearings after a run of 30 km or more. The flange nut should be tightened to a torque of 12-26 kgf·m, periodically checking the moment of resistance of the bearings to turning the drive gear. To check the moment of resistance, put the dynamometer on the adapter sleeve and make a few turns clockwise with the handle. While turning the drive gear, the movable dynamometer indicator should not go beyond the limiter and should show at least 16 kgf cm. If the moment of resistance to rotation is less than 16 kgf cm (4 kgf cm for bearings after 30 km run), it is necessary to tighten the drive gear flange nut (without exceeding the specified tightening torque) and check again the moment of resistance to turning the drive gear. If the moment of resistance to rotation turned out to be more than 20 kgf cm (6 kgf cm for run-in bearings), this indicates an excessive bearing preload. In this case, it is necessary to replace the spacer sleeve, as it has been deformed to a size due to excessive load that does not allow for correct adjustment. After replacing the spacer sleeve, repeat assembly with appropriate adjustments and checks.
Installing the differential box
Install the pre-assembled gearbox into the gearbox housing together with the outer races of the bearings, two adjusting nuts 1 (pic. 137), so that they are in contact with the bearing rings and the bearing caps. Then tighten the mounting bolts.
Preload the bearings of the differential box and adjust the backlash in the meshing of the final drive gears at the same time using tool A.95699/R and wrench 12 (A.55085). To do this, fix the fixture on the gearbox housing with screws 11 and screw them into the holes for the bolts for fastening the locking plates of the adjusting nuts. Move indicator bracket 4 along the fixture guide until lever 2 touches the outer side surface of the cover and tighten screw 5.
Loosen the screws 7 and 9 and install the bracket 10 so that the indicator leg 8 rests on the side surface of the driven gear tooth at its edge, then tighten the screws.
Turning the adjusting nuts, pre-adjust the lateral clearance between the teeth of the gears within 0.08-0.13 mm according to indicator 8 while rocking the driven gear 13. In this case, the bearings should not have a preload. The adjusting nuts must only be in contact with the bearings, otherwise the correct preload measurement will be impaired.
Tighten the two adjusting nuts 1 and 2 in sequence and evenly (pic. 138) bearings. In this case, the differential bearing caps diverge and the distance A increases. This discrepancy is indicated by indicator 6 (see fig. 137), on the leg of which the lever acts 2. Tighten the nuts for adjusting the bearings of the differential box until the distance A increases (see fig. 138) by 0.14-0.18 mm. Having set the exact preload of the bearings of the differential box, finally check the backlash in the meshing of the final drive gears, which should not change. If the gap in the meshing of the gears is more than 0.08-0.13 mm, then bring the driven gear closer to the leading one. If the gap is smaller, move it back.
To maintain the set bearing preload, move the driven gear by tightening one of the bearing adjusting nuts and loosening the other by the same angle. To accurately perform the operation, you must follow the indicator 6 (see fig. 137), which shows the previously set bearing preload.
After tightening one of the nuts, the indicator reading will change as distance A increases (see fig. 138) and bearing preload. Therefore, loosen the other nut until the indicator needle returns to its original position. After moving the driven gear on the indicator 8 (see fig. 137) check the side clearance. If the clearance is not correct, repeat the adjustment.
After adjustment, remove tool A.95688/R, install the locking plates of the adjusting nuts and secure them with bolts and spring washers. Spare parts are supplied with locking plates in two types: with one and two tabs. One or the other plate is installed depending on the position of the nut slot.
Checking the contact of the working surface of the gear teeth
To check the quality of gear engagement:
- install the adjusted gearbox on the stand and lubricate the working surfaces of the teeth of the driven gear with a thin layer of lead oxide;
- start the stand and use its levers to slow down the rotation of the axle shafts so that under load on the surfaces of the teeth of the driven gear there are traces of contact with the teeth of the drive gear;
- change the direction of rotation and, when braking, get contact marks on the other side of the teeth of the driven gear, which corresponds to the movement of the car in reverse.
Engagement is considered normal if on both sides of the teeth of the driven gear the contact patch is evenly located closer to the narrow end of the tooth, occupying 2/3 of its length and not reaching the top of the tooth base, as shown in Fig. 139, d.
To adjust the correct position of the drive gear with the replacement of the ring, disassembly of the assembly is necessary. When assembling, it is necessary to repeat all the operations for preloading the drive gear bearings, checking the moment of resistance to rotation, preloading the bearings of the differential box and adjusting the backlash of the final drive gears.