The front axle arrangement is shown in fig. 1.
The main gear and differential of the rear and front drive axles are the same, with the exception of the oil receiving device for the drive gear shaft bearings, which is not used in the front axle
In the front axle, a constant-velocity cardan is used.
The rectangular front axle housing consists of two halves, stamped from sheet steel, welded along the horizontal axis of the axle.
The middle part of the crankcase is shifted relative to the longitudinal axis of the car to the left, butt-welded flanges are butt-welded at the ends, to which the ball bearings of the pivot pins are attached.
Front axle maintenance
Care of the front axle in operation consists in maintaining the required oil level in the crankcase and its periodic change, lubricating the universal joint of constant angular velocity and kingpins, periodically checking the condition of the tightening of the kingpin bearings, checking the toe-in of the wheels, tightening loose connections, checking the condition of tightening the bearings of the drive shaft gears.
The engagement is adjusted only when installing new gears.
Faults, their causes and remedies in the main gear and differential of the front axle and rear axle are similar.
Front axle repair
Removing the front axle from the car. To remove the front axle, you must:
Disconnect the flexible hose on the left stringer from the hydraulic brake lines. Unscrew the flexible hose from the front axle.
Additionally for GAZ-66-01 car:
- - disconnect the hose on the right longitudinal beam from the pipeline of the tire pressure control system, unscrew the flexible air supply hose from the front axle;
- - disconnect the shock absorbers from the front axle;
- - disconnect the pipelines and flexible hoses from the power steering control valve, from the tie rod, from the front axle and from the power steering power cylinder;
- - disconnect the front propeller shaft from the flange of the front axle drive gear shaft;
- - disconnect the longitudinal link from the steering arm;
- - remove pads, stepladders and front spring covers;
- - roll back the front axle and install it on a stand or stands.
Dismantling the front axle
Disconnect the tie rod from the stub axle arm.
Remove footpegs. For the car GAZ-66-01 additionally:
- disconnect the air supply pipeline to the air valve from the front axle hub flange cover and from the valve.
Remove the protective cover, wheels, brake drum and protective cap of the clutch.
With a special key, unscrewing the bolt of the coupling of the leading flange, remove the coupling (at the same time, make sure that the stopper with the spring does not fall out of the hole in the cardan shaft).
Remove the drive flange (do not remove the studs when removing the flange). For the GAZ-66-01 car, additionally remove the hub flange cover.
Remove the hub with bearings.
Disconnect the hydraulic brake lines from the brake disc.
For the GAZ-66-01 car, additionally disconnect the flexible hoses for supplying air to the sealing unit passing through the brake discs.
Remove the brake shield with oil deflector and pin.
For GAZ-66-01 vehicles, additionally remove the hub seal and unscrew the flexible air supply hose to the seal block from the seal block.
Remove the CV joints.
Compress the ball joint with the dismantling bolts. Remove the lever on the left stub axle housing and shim set.
Remove the top cover plate of the right pivot pin with a set of shims.
Remove the lower king pins with a set of shims.
Remove the ball joint seal.
Remove the outer races of the kingpin bearings.
Remove the bearings from the ball joint pivots.
Disconnect ball joint and stub axle housing.
Front axle problems and how to fix them
Causes of malfunction - remedies
Violation of the correct camber angle, the appearance of "wobble" of the front wheels when driving and uneven tire wear due to large clearance in the front wheel hub bearings - Adjust the front wheel hub bearing preload
The vehicle does not hold the road well due to deflection of the front axle housing - Straighten the housing or replace the axle housing with a new one
Lubricant leakage through the rubber-felt oil seal of the stub axle due to its wear - Replace the oil seal
Increased tire wear due to misalignment of the wheels (bend of the linkage or incorrect setting of its length) - Correct traction or break adjust its length
Disassembly of CV joints
If necessary, the CV joint is disassembled in the following order.
Mark with paint or chalk the relative position of the cardan forks.
Put the universal joint in a vertical position with the short (driven) fork up so that the pin of the central ball under the action of its own weight can lower into the drilling of the central ball.
If the pin does not go down, then knock the end of a long fork on a wooden stand or spread the forks and lower the pin with a screwdriver.
Turn the center ball together with the pin and remove the pin.
Turn the central ball flat towards one of the leading balls, bend the driven fork, while one of the leading balls opposite the flat can be removed from the cardan.
The rest of the balls, after the first one is taken out, are taken out freely.
The requirements for the technical condition and permissible wear of the parts of the front and rear axles are similar.
Front axle assembly
Assembly of CV joints. Cardans are assembled after selection of new oversized repair balls or as a result of replacing one of the forks.
The assembly order is as follows.
Clamp the drive (long) fork in a vertical position (with the fork up).
Install the center ball (without the pin) in the spherical recess of the drive fork with the flat to the side.
Put the driven fork on the center ball.
Turning the fork to the side, install three leading balls alternately into the grooves of the forks.
Spreading the cardan forks to the maximum angle and turning the central ball flat towards the groove of the fourth drive ball, insert this ball into the groove so that it goes past the flat.
Spreading the forks, insert the pin into the hole of the central ball.
Turn the center ball so that the axis of the center ball pin aligns with the hole in the driven fork. Move the forks so that the end of the pin enters the hole in the fork
Longitudinal movements of the cardan of equal angular velocities in the bridge are limited by thrust washers, one of which is installed in the ball bearing, and the other in the trunnion.
The preload in the cardan balls should be such that the moment required to turn the fork 10-15˚ in all directions from the vertical with the other fork clamped in a vice is 500-800 kgcm.
In order to ensure correct assembly and obtain the required preload, the drive balls are sorted into nine groups according to diameter sizes (mm):
- 1st group - 40.09 - 40.07
- 2nd - 40.07 - 40.05
- 8th - 40.05 - 40.03
- 4th - 40.03 - 40.01
- 5th - 40.01 - 39.99
- 6th - 39.99 - 39.97
- 7th - 39.97 - 39.95
- 8th - 39.95 - 39.93
- 9th - 39.93 - 39.91
Setting ball diameter, mm 34.85 ± 0.025.
Each gimbal is assembled with balls of one group or two adjacent groups. For example, two balls with a diameter of 39.98 mm and two with a diameter of 40.00 mm.
When mounting, balls of the same size must be placed diametrically opposite to one another.
The difference in the diameters of two pairs of balls of one cardan is allowed no more than 004 mm.
The cardan is run on the stand at a changing angle of the forks from 0 to 30 ° for 2 - 3 minutes at 150 rpm.
When running in, the cardan shaft is lubricated with oil.
The front axle is assembled in the reverse order of disassembly. Please note the following when assembling:
Press the sleeve into the ball joint of the pivot pin flush with the end of the socket under the thrust washer.
For GAZ-66-01 vehicles, screw a flexible hose into the stuffing box before installing the stub axle.
When assembling and installing the stub axle oil seal, soak the felt outer ring in warm engine oil.
When placing equal angular velocities in the cardan, apply grease to the ball joint according to the lubrication chart.
Lubricate the pivot bearings through the grease fittings according to the lubrication chart.
The front axle after assembly is checked on the bench without load and with load. A properly assembled front axle must meet the following requirements.
During the operation of the bridge, increased noise and increased heating should not be observed.
There must be no oil leakage through the stuffing box, covers and bolted connections.
Tighten the nuts of the studs securing the drive flange to the hub (torque 12-14 kgm).
Front axle adjustment
The bearings of the drive gear shaft, differential, hub and gear engagement of the main gear in the front axle are adjusted in the same way as in the rear axle.
Adjusting the tightening of the pivot pin bearings.
Before checking the tightness of the kingpin bearings, check the tightness of the wheel bearings. The tightening of the pivot bearings is checked with the wheels hung on the jack and the steering rods removed.
When checking, shake the wheels with your hands in a vertical plane in several positions within the angle of rotation of the wheel on the pivot.
The kingpin bearings must be adjusted so that there is absolutely no play in them, otherwise the bearings will be quickly destroyed.
Shims 0.10 and 0.15 mm are used to adjust the kingpin bearings.
Factory adjusted bearings have the same number and thickness of shims on top and bottom.
When adjusting the pivot bearings, be sure to remove the same number of spacers from above and below, otherwise the alignment of the pivot pin parts will be disturbed.
With properly adjusted bearings, the stub axle should rotate relative to the kingpins by hand with little effort.
When checking with a dynamometer, the force applied to the swivel arm of the lateral steering rod, in the place of the ball pin, with the ball bearing seals removed, with the front axle raised on the jack, the steering rods removed and the universal joint of equal angular speeds removed, should be equal with a smooth movement of the dynamometer 2.25 - 3.75 kg.
When adjusting the upper kingpin on the left side of the front axle, before removing the tie rod arm, disconnect the flexible hoses of the brake system and the tire pressure control system.
Never unscrew the studs to remove the pivot arm.
Checking the alignment of the front wheels
In order to ensure the stability of the vehicle and eliminate increased tire wear, the installation of the front wheels indicated in the table is provided (Fig. 2).
Front wheel alignment
Installing the front
pivot ends forward
2 – 5 mm
In the car, only the toe-in is regulated. The angles of inclination of the kingpins and the camber of the wheels are not regulated, but are provided by the design of the front axle.
In operation, these angles may be violated in case of wear of parts, deflection of casings from impacts during an accident or breakage of springs.
Camber angle - the angle between the plane of the wheel and a vertical plane parallel to the longitudinal axis of the car, increases the stability of the car while driving.
This angle may be violated due to the looseness of the wheel bearings or the deflection of the casings of the axle shafts and the ball joint.
The camber angle is checked with instruments. In the absence of instruments, you can measure with a square the dimensions between the vertical plane of the square and the lower or upper end of the wheel rim.
The difference in dimensions corresponding to a given camber angle of 0˚45' should be 4-9 mm.
To measure, a fully loaded vehicle is placed on a level surface with normal tire pressure and a straight-line wheel position.
Toe-in is measured by the difference in distance between the inner surfaces of the tires at the rear (B) (see Fig. 2) and front (A) approximately at the level of the centers of the wheels.
This difference, with the correct toe-in, should be 2-5 mm, i.e. B-A = 2-5 mm.
Toe-in is adjusted by changing the length of the tie rod. To do this, loosen the tension ku of the bolts of the tips and, squeezing the left or right finger of the thrust from the lever of the body of the pivot pin, rotate the tip, achieving a convergence of 2-5 mm.
To ensure adjustment within the specified limits, the tips have different thread pitches (left - 2 mm, right - - 1.5 mm).
When adjusting the toe-in, maintain the dimension З63 ± 1 mm from the center of the ball pin of the right tip to the end of the base of the bracket for fastening the rod of the power steering cylinder, as violation of this dimension will cause incorrect operation of the power cylinder.
At the end of the adjustment, tighten the nuts of the handpiece bolts, tighten the handpiece finger nut and cotter.
When adjusting and final tightening of the tie rod ends, ensure a clearance (30 mm) between the tie rod and the front axle drive gear shaft bearing cover.
This clearance is necessary to prevent the transverse link from touching the axle gearbox housing when the wheels are turning.
Toe-in is checked under the same conditions under which the camber angle is checked.
Used hub bearings
Front wheel bearings:
- - internal - 7515 (inner diameter 75, outer diameter 130, width 33.5 mm);
- - outer - 807813K1 (inner diameter 65, outer diameter 110, width 30.5 mm).