The design of the final drive of the drive axles is shown in Figure 1.
One of the characteristic signs indicating the need to disassemble and adjust the gearbox is increased noise when the vehicle is moving.
Causes of increased noise:
- - displacement of the contact pattern in the engagement of bevel gears as a result of improper adjustment of tapered roller bearings;
- - scoring and chipping of gear teeth, bearing wear, as well as insufficient oil level in the axle housing.
The vehicle's drive axles are of the through type, with the final drive located at the top.
The final drive of the axle is double-stage, consisting of a pair of bevel gears 1 and 14 (Fig. 3) with spiral teeth and a pair of cylindrical gears 4 and 29 with helical teeth.
A symmetrical bevel differential with four pinions is bolted to the driven cylindrical gear.
Depending on the technical requirements of the vehicle, the final drives have gear ratios of 7.32; 6.7; 8.9 and 8.05.
To distinguish them, the final drives are marked with plates indicating the gear ratio, installed under the bolt securing the cover of the bearing cup of the driving cylindrical gear.
Final drives with a gear ratio of 8.9 have no marking plates.
The gears of the final drives are distinguished by marks on the driving and driven cylindrical gears (see table).
Table 1. Marking of final drive gears
Gear ratio 6.7:
- - marks on the end of the driving cylindrical gear on the bevel gear side - two drillings ∅ 10 mm at a distance of 12 mm from the edge to a depth of 2 mm;
- - mark on the driven cylindrical gear - chamfers on both sides under the gear rim
Gear ratio 7.32:
- - marks on the end of the driving cylindrical gear on the bevel gear side - one drilling ∅ 10 mm to a depth of 2 mm;
- - mark on the driven cylindrical gear - one chamfer under the gear rim
Gear ratio 8.05:
- - marks on the end of the driving cylindrical gear on the bevel gear side - a cylindrical groove ∅ 52 mm;
- - mark on the driven cylindrical gear - a line on the end ∅ 290 mm
Gear ratio 8.9:
- - marks on the end of the driving cylindrical gear on the bevel gear side - none;
- - mark on the driven cylindrical gear - none
The final drive is installed on the axle housing 10 (Fig. 4) through a paronite sealing gasket 9 with a thickness of 0.8 mm and is secured using eleven bolts and two studs.
Eleven bolts and studs are installed on the outside, and two bolts are located in the cavity of the bevel gears.
Access to the inner bolts is possible only after removing the side cover 6.
Spring washers are installed under the outer bolts and nuts of the studs.
The inner bolts are cotter pinned with wire.
The gears and bearings of the final drive are lubricated with oil poured into the axle housing and the final drive housing up to the level of the inspection hole.
The oil is picked up by the gears, splashed, and through the roller bearing 2 (see Fig. 3) enters the cavity of the bevel gears of the final drive housing, from where it drains into the axle housing.
The bearings of the driving bevel gear are lubricated with oil from the cavity of the bevel gears, which is supplied to the bearing cup through a pocket on the housing cover and an oil supply fitting.
The final drives of the front and rear axles differ from the final drive of the middle axle by their drive flanges.
A bush 21 with a cover 22 is installed on the front end of the driving gear shaft of the front axle, and a flange 18 on the rear end.
The final drive of the rear axle has one flange on the side of the driving bevel gear.
Splines may not be made on the opposite end of the driving gear shaft.
The housings 10 (see Fig. 4) of the axles are combined, consisting of a cast middle part and tubular axle shaft casings pressed into it.
The axle shafts are fully floating, the connection of the axle shaft to the hub is splined.
The front axle of the vehicle is a drive steered axle. The design of the kingpin assembly of the front drive axle is shown in Fig. 5.
Torque is transmitted to the front drive wheels through the axle shafts and constant velocity joints (Fig. 6).
For reliable and durable operation of the drive axles, use oils according to the lubrication chart and maintain the required level in the housings.
To replace the lubricant in the front axle shaft joints, remove the wheel, the brake drum with the hub, the brake shield, and the steering knuckle pin. Remove the lubricant and wash the constant velocity joint parts.
Regularly check the tightening of the bolts securing the final drive to the axle housing.
Loosening the bolts causes the housing to bend.
Oil change in drive axle housings and checking its level
Clean the drive axle housing from dust and dirt.
Unscrew the plug 3 (Fig. 7) of the inspection hole and the drain plug 4 in the housing, drain the oil (it is advisable to drain it immediately after stopping the vehicle, when it is still warm).
Screw in the drain plug. Unscrew the hose 5 from the fitting 2 of the sealing system, clean it with a wire brush and screw it in.
Flush the axle housing by pouring 1.5–2 litres of low-viscosity oil into it.
Drain the low-viscosity oil and pour 13.5 litres of clean TSp-15k (MT-16p) transmission oil into the housing.
The oil should be changed alternately in all drive axles.
Check the oil level in the drive axle by unscrewing the plug of the inspection hole.
The oil should be at the level of its lower edge.
The filler hole, closed with plug 1, is used when filling the axle with oil after replacing the bevel gears.
Check the tightness of the connections and the absence of oil leaks.
Tighten the bolts 1 (Fig. 8) securing the gearbox, bolts 2 and 3 of the through shaft covers and bolts 4 of the final drive bearing cups. There should be no traces of oil leaks on the surface of the housing and at the joints.
Lubrication of the front axle shaft joints and lower kingpin bearings
Unscrew the plug 1 (Fig. 9) of the filler hole of the steering knuckle housing and check the presence of lubricant. It should be at the level of the filler hole.
If the level is insufficient, add the heated mixture consisting of 50% AM grease (universal) and 50% TSp-15k, and pour it into the steering knuckle housing to the required level.
Screw in the plug.
To replace the lubricant in the constant velocity joints of the front drive axle, disassemble the joints, remove the old lubricant, wash the joint parts.
Place the fresh lubricant directly inside the ball joints.
Lubricate the upper kingpin bearings through the grease nipple 2 using a grease gun.
