MAZ gearbox adjustment

Adjusting the central gearbox

Adjust with the gearbox removed in the following sequence:

• —adjust the tightness of the tapered bearings of the drive bevel gear;
• —adjust differential bearings;
• —adjust the meshing of the bevel gears according to the contact patch and backlash, then adjust the differential bearings.

At the same time, in order to avoid violating the initial adjustment of the bearings, nuts 17 fig. 1 unscrew and wrap at the same angle.

To adjust the bearings of the drive bevel gear, remove the drive bevel gear with the bearing housing assembly, to do this, in the rear axle gearbox housing, unscrew the bolts securing the cup 12 (see Fig. 1) of the bearings and use the dismantling bolts to remove the cup 12 with the gear.

In the middle axle gearbox, unscrew the bolts securing the gear housing and using dismantling bolts remove the gear housing assembly with the input shaft, bend the locking plates, unscrew the nuts securing the bearing cup and remove the bearing cup assembly with the drive bevel gear;

• —determine the axial clearance in the bearings with the indicator;
• - fix the drive gear in a vise, protecting it from damage with soft metal gaskets;

• - remove flange 6 (see Fig. 1), cover 9 with seals 4, 5 or gear 10 (see Fig. 2), inner ring of the bearing closest to the shank and adjusting shim 2 (see Fig. 1) ;
• - measure the thickness of the shim and calculate the required thickness to eliminate the axial play and obtain a preload of the bearings (the decrease in the thickness of the shim should be equal to the sum of the axial play measured by the indicator and the bearing preload value equal to 0.03-0.05 mm);
• - grind the shim to the required size and assemble the drive gear without fixing the cover with cuffs;
• —when tightening the flange nut, rotate the bearing cup to properly position the rollers in their cages;
• - check the bearing preload according to the torque of the bearing cup rotation, which should be equal to 1-3 Nm (0.1-0.3 kgf-m) (Fig. 3).

With normal preload in the bearings, remove the flange 6 (Fig. 1), replace the cover 9 with the stuffing box and finally assemble the assembly.

Adjust the tightness of the differential bearings with the drive gear removed using nuts 17 (see Fig. 1) and 50 (see Fig. 2).

Turn the nuts to the same depth until the desired preload is obtained, without disturbing the position of the driven gear using a special wrench (Fig. 4).

The bearing preload is determined by the amount of torque required to rotate the differential, which should be within 2-5 Nm (0.2-0.5 kg / cm with the drive gear removed).

This moment is determined by a special torque wrench or by measuring the force applied on the radius of the differential cups and equal to 23-57 N (2.4-5.8 kgf).

The procedure for checking and adjusting the meshing of bevel gears is as follows:

• - before installing the bearing housing with the drive gear into the gearbox housing, wipe the teeth of both bevel gears and apply a thin layer of paint on the side surfaces of three or four teeth;
• - according to the table, adjust the meshing of the bevel gears. The movement of the drive gear is provided by changing the number of shims under the flange of the cup of the drive gear bearings.

To move the driven gear, use nuts 17 (see Fig. 1) or 50 (see Fig. 2), in order not to disturb the adjustment of the preload in the differential bearings, turn (unscrew) these nuts at the same angle.

Adjust bearings 13 in the following sequence:

• —disconnect cardan shaft from flange 17;
• - remove the differential lock mechanism;
• - unscrew the bolts securing the gear housing and remove the housing assembly with the center differential;
• - disassemble the center differential, remove the drive gear and remove the bearings from the gear;
• - wash the parts in diesel fuel, and lubricate before assembly;
• - install the inner bearing in the gear seat 26;
• - install the spacer ring 25 and the outer race of the outer bearing;
• -- to provide pre-th preload in the bearings, reduce the thickness of the set of washers 22 by the value of the axial clearance plus 0.02-0.03 mm and install them in place;
• —install the inner race of the bearing assembly with the cage.

To check the preload in the bearings, install gear 26 with bearings on the press table through the mandrel (with support on the end of the inner race of the inner bearing) and compress the bearings with a slight force.

As a mandrel, you can use the cross 28 and the spacer 27 assembled with the gear. By rocking, check the presence of axial clearance and the ease of turning the gear.

The turning force of the driving spur gear applied on its outer diameter should be in the range of 5.4-22N (0.55-2.2kgf).

The bearings 37 of the output shaft 33 are also adjusted by changing the set of shims 42 in the following sequence:

• - unscrew the bolts 39 and remove the output shaft 33 with a glass of bearings;
• — wash parts in diesel fuel and lubricate before assembly;
• — clamp the shaft in a vise, install the inner race of the inner bearing with the cage on the shaft;
• - install cup 36 complete with outer bearing races;
• - install the required set of shims 42, the thickness of which is reduced by the value of the axial clearance plus 0.02-0.03 mm;
• - install the separator and the inner race of the outer bearing;
• - install flange 41, tighten the nut. Check for axial play by rocking and turning the flange 41.

The turning force applied at the radius of the holes in the flange should be in the range of 6.4-25.5 1-1 (0.65-2.6 kgf).

After adjustment, unscrewing the nut and removing the flange 41, install the stuffing box cover 38 and, having assembled the assembly, tighten the flange nut. In this case, the holes for the cotter pin must match the slot in the nut. Then cotter the nut, reinstall the shaft with the bearing assembly and the flange assembly.

Adjusting the interwheel and center differential locking mechanisms

The cross-axle differential locking mechanism is adjusted on the assembled central gearbox, before installing it in the axle housing, in the following order (Fig. 1):

• —measure the gap between the ends of the clutch 24 and the differential cup, the value of which should be 10.5 mm, while the clutch 24 should be held coaxially with the cup 23 using a mandrel;

• - unscrew the bolts of the pneumatic cylinder 26 and remove it together with the piston;
• - After unscrewing the yoke stem screw nut, tighten or unscrew the screw by the amount of fork travel required to provide a gap of 10.5 mm, tighten the nut and install the cylinder.