Fault detection and assembly of the rear gearbox VAZ-2123

Before inspecting the gearbox parts, wash them thoroughly.

This will make it easier to detect wear and damage to the parts.

Check the main gear teeth for damage and whether the contact spots on the working surfaces of the teeth are located correctly.

If the parts are worn beyond acceptable limits, replace them with new ones; if the engagement is incorrect, find the cause.

The drive and driven gears are supplied as a set in the spare parts store, selected based on noise and contact, so if one gear is damaged, replace both.

Check the condition of the satellite holes and their axle surfaces; in case of minor damage to the surface, sand it with fine-grained sandpaper, and in case of serious damage, replace the parts with new ones.

Check the surfaces of the axle shaft gear journals and their mounting holes in the differential box, the condition of the holes in the box for the satellite axle.

Remove any damage found as in the previous operation, replace worn or damaged parts if necessary.

Inspect the surfaces of the axle shaft gear support washers, repair even minor damage. When replacing washers, select new ones by thickness.

Inspect the roller bearings of the pinion gear and differential box; they must be free of wear, with smooth working surfaces.

Replace the bearings if there is the slightest doubt about their performance; poor condition of the bearings can be the cause of noise and tooth seizure.

Check the crankcase and differential box for deformations or cracks, replace them with new ones if necessary.

Assembling the gearbox

Reliable operation of the gearbox is ensured by strict adherence to the following assembly and adjustment techniques.

The gearbox parts are shown in Figure 1.

Differential assembly

Lubricate with transmission oil and install the axle shaft gears with support washers and satellites through the windows into the differential box.

Turn the satellites and axle shaft gears so as to align the rotation axis with the hole axis in the box, then insert the satellite axis.

Check the axial clearance of each axle shaft gear: it should be 0-0.10 mm, and the torque of resistance to rotation of the differential gears should not exceed 14.7 Nm (1.5 kgfm).

If the clearance is increased, which is a sign of wear of the differential parts, replace the support washers of the axle shaft gears others, of greater thickness.

If the specified clearance cannot be obtained even when installing the thickest washer, replace the gears with new ones due to their excessive wear.

Fasten the driven gear on the differential case.

Use the A.70152 mandrel to press the inner rings of the roller bearings onto the differential case.

Installing and adjusting the drive gear

The correct position of the drive gear relative to the driven gear is ensured by selecting the thickness of the adjusting ring installed between the end of the drive gear and the inner ring of the rear bearing.

Select the adjusting ring using the A.70184 mandrel and the A.95690 device with an indicator.

Perform the operations in the following order.

Having secured the gearbox housing on the stand, press the outer rings of the front and rear bearings of the drive pinion into the housing seats, using mandrels for this: for the front bearing A.70185, and for the rear - A.70171 (Figure 2).

On the mandrel A.70184, simulating the drive gear, install the inner ring of the rear bearing using the mandrel A.70152 and insert the mandrel into the neck of the gearbox housing (Figure 3)

Install the inner ring of the front bearing, the flange of the drive gear and, turning the mandrel for the correct installation of the bearing rollers, tighten the nut with a torque of 7.85-9.8 Nm (0.8—1 kgf/cm).

Fasten the device A.95690 on the end of the mandrel 4 and set the indicator, which has divisions of 0.01 mm, to the zero position by installing its leg on the same end of the mandrel A.70184.

Then move the indicator 1 so that its leg stands on the seating surface of the differential box bearing.

By turning mandrel 4 with an indicator left and right, set it to a position in which the indicator arrow marks the minimum value "a 1" (Figure 4) and write it down.

Repeat this operation on the seating surface of the second bearing and determine the value "a2".

Determine the thickness "S" of the adjusting ring of the drive gear, which is the algebraic difference of the values ​​"a" and "b":

S = a - b, where:

• a is the average arithmetic distance from the end of the mandrel 1 (Figure 4) to the journals of the differential bearings
• a = (a1 + a2) : 2
• b — deviation of the drive gear from the nominal position translated into mm.

The deviation value is marked on the drive gear (Figure 5) in hundredths of a millimeter with a plus or minus sign.

When determining the thickness of the adjusting ring, take into account the sign of the value "b" and its units of measurement.

Example

Let's assume that the value "a", set using the indicator, is 2.91 mm (the value "a" is always positive), and on the drive gear after the serial number, the deviation "-14" is indicated.

To obtain the value "b" in millimeters, you need to multiply the specified value by 0.01 mm.

b = -14 · 0.01 = -0.14 mm

Determine the thickness of the adjusting rings for the pinion gear in millimeters.

S = a – b = 2.91 – (–0.14) = 2.91 + 0.14 = 3.05 mm

In this case, install an adjusting ring with a thickness of 3.05 mm.

Put an adjusting ring of the required thickness on the drive pinion and press on the inner ring of the rear bearing, removed from the A.70184 mandrel, using the A.70152 mandrel (Figure 6).

Put on the spacer sleeve.

When repairing the rear axle reducer, it is necessary to install a new spacer sleeve if the reducer housing, final drive gears or drive pinion bearings have been replaced.

If the specified parts remain the same, the spacer sleeve can still be used.

Insert the drive pinion into the reducer housing and install the inner ring of the front bearing, oil deflector, oil seal, drive pinion flange and washer on it.

Screw onto the end gear nut and, having locked the flange of the drive gear, tighten it.

Adjusting the bearings of the drive gear

To limit 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 the dynamometer 02.7812.9501 (Figure 7), which measures the torque resistance of the drive gear.

The torque resistance determines the degree of bearing tightening.

It should be 157–196 N cm (16–20 kgf cm) for new bearings, 39.2–58.8 N cm (4–6 kgf cm) – for bearings after a run of 30 km or more.

The flange nut should be tightened periodically, checking the moment of resistance of the bearings to turning the pinion gear with a dynamometer.

In this case, the moment on the nut can be within 118–255 N m (12–26 kgf m).

To check the moment of resistance, put the dynamometer on the adapter sleeve 3 (Figure 8), set the pointer 2 (see Figure 7) of the torque limitation to the division of the scale corresponding to 196 N cm (20 kgf cm), and make several turns clockwise with the handle 4.

When turning the drive gear, the movable pointer 1 should not go beyond the pointer 2 and should show at least 157 N cm (16 kgf cm).

If the moment of resistance to turning is less than 157 N cm (16 kgf cm), and for bearings after 30 km of travel 39.2 N cm (4 kgf cm), then tighten the nut of the flange of the drive gear gears (without exceeding the specified tightening torque) and check the turning torque of the pinion gear again.

If the turning torque is more than 196 N cm (20 kgf cm), and for worn-in bearings 58.8 N cm (6 kgf cm), which indicates that the bearing preload is too high, replace the spacer sleeve with a new one, since it has been deformed due to excessive load to a size that does not allow correct adjustment.

After replacing the spacer sleeve, repeat the assembly with the appropriate adjustments and checks.

Installing the differential case

Install the pre-assembled differential case into the crankcase together with the outer bearing rings.

Install two adjusting nuts 4 (Figure 9) so that they touch the bearing rings.

Install the bearing caps and tighten the mounting bolts with a torque wrench.

Preloading the differential box bearings and adjusting the side clearance in the main gear engagement

These operations are performed simultaneously using the A.95688/R device and the A.55085 key.

Fasten the device to the gearbox housing with screws 1 and 6, screwing them into the holes for the mounting bolts of the adjusting nuts lock plates.

Move bracket 7 along the guide of the device until lever 5 touches the outer side surface of the cover and tighten screw 8.

Loosen screws 1 and 3 (Figure 10) and install bracket 4 so that the indicator leg 2 rests on the side surface of the driven gear tooth at the edge of the tooth, then tighten screws 1 and 3.

By turning the adjusting nuts, pre-adjust the lateral clearance between the teeth of the driving and driven gears within 0.08–0.13 mm.

Check the clearance using indicator 2 while rocking gear 6. In this case, the bearings should not have a preload.

The adjusting nuts should only be in contact with the bearings, otherwise the preload measurement will be incorrect.

Tighten the two bearing adjusting nuts in sequence and evenly, thus increasing the differential bearing caps and, consequently, increasing the distance "D" (Figure 11) by 0.14-0.18 mm.

Having set the exact preload of the differential box bearings, finally check the side clearance in the engagement of the main gear gears, which should not change.

If the clearance in the engagement of the gears is more than 0.08-0.13 mm, then bring the driven gear closer to the driving gear or move it away if the clearance is smaller.

To maintain the set preload of the bearings, move the driven gear by tightening one of the bearing adjusting nuts and loosening the other by the same amount. angle.

To perform this operation accurately, watch the indicator 9 (see Figure 9), which shows the value of the previously set preliminary load of the bearings.

After tightening one of the nuts, the indicator reading will change, since the divergence "D" (see Figure 11) of the covers and the preliminary load of the bearings increase.

Therefore, loosen the other nut until the indicator arrow returns to its original position.

After moving the driven gear, check the lateral clearance using indicator 9 (see Figure 9). If the clearance is not within the standard, repeat the adjustment.

Remove the A.95688/R device, install the adjusting nut locking plates and secure them with bolts and spring washers.

Spare parts come in two types of locking plates: with one or two tabs, depending on the position of the nut slot.

Adjustment and repair of gearbox units is performed on a stand, where you can also test the gearbox for noise and check the location and shape of the contact patch on the working surfaces of the teeth, as indicated below.

Checking the contact of the working surface of the teeth of the main gear

For a final check of the quality of the engagement of the main gear on the stand:

• - 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 stand, use the stand levers to slow down the rotation of the installed axle shafts so that under loads, traces of contact with the teeth of the driving gear remain on the surfaces of the teeth of the driven gear;
• - change the direction of rotation of the stand and, braking, get traces of contact on the other side of the teeth of the driven gear, which corresponds to the backward movement of the car.

The engagement is considered normal if on both sides of the teeth of the driven gear the contact patch is evenly distributed closer to the narrow end of the tooth, occupying two-thirds of the length and not extending to the top and base of the tooth, as shown in Figure 12

Cases of incorrect location of the contact spot on the working surface of the tooth are shown in Figure 12 (2, 3, 4, 5).

To adjust the correct position of the driving gear with replacement of the ring, it is necessary to disassemble the unit.

During assembly, repeat all operations for pre-tensioning the roller bearings of the driving gear, checking the torque of resistance to rotation, pre-tensioning the roller bearings of the differential box and adjusting the side clearance of the main gear engagement gears.