Repair and maintenance of the front axle UAZ-3151
The main gear and differential of the front axle are similar in design to the rear axle
All maintenance and repair instructions for the rear axle also apply to the front axle
Additionally, the steering knuckles are serviced and repaired (Fig.1).
Fig. 1. Steering knuckle
When servicing the front drive axle, check and, if necessary, adjust the tightness of the kingpin bearings, toe-in and maximum steering angles, check and tighten the steering knuckle lever fastening, flush and change the grease in the steering knuckles.
When inspecting the steering knuckles, pay attention to the serviceability of the stops-limiters 28 (Fig.1) for turning the wheels, adjusting bolts 27 and the reliability of their locking.
Check and adjust the axial clearance of the pivots on the car in the following order:
Brake the vehicle with the parking brake or chock the rear wheels.
Raise the front axle with a jack.
Unscrew the wheel nuts and remove it.
Remove the bolts securing the ball joint seal and move the gland.
Fig. 2. Checking the adjustment of the pivots: 1 - top pad; 2 - adjusting gasket; 3 - kingpin; 4 - bottom overlay
Check the axial clearance of the pivots by rocking the steering knuckle housing up and down with your hands (Fig. 2).
Unscrew the nuts of the studs of the lever 1 (see Fig.1) of the steering knuckle or the bolts of the upper lining 1 (see Fig. 2) and remove the lever or the upper lining of the kingpin.
Remove the thin (0.1 mm) shim and install the lever or trim in place.
Remove the mounting bolts and remove the bottom pad of the 4th kingpin, remove the thin (0.1 mm) shim and install the kingpin pad in place.
To maintain the alignment of the hinge, remove the spacers of the same thickness at the top and bottom.
Check the build results.
If the gap persists, readjust by removing thicker shims (0.15 mm).
Large wear of pins 9 and bushings 19 (see Fig. 1) in diameter causes a violation of the camber angle of the wheels, their “wobble” when driving and uneven tire wear. In this case, replace the worn parts.
Fig. 3. Checking the maximum steering angles
Check the maximum angles of rotation of the wheels on a special stand (Fig. 3).
The angle of rotation of the right wheel to the right, and the left wheel to the left must be no more than 27 °. Adjust with bolt 27 (see Fig.1).
Toe-in adjust by changing the length of the tie rod.
Before adjusting, make sure there are no gaps in the tie rod joints and hub bearings; then, loosening the lock nuts (having right and left threads), turn the adjusting nipple to set the required wheel toe-in.
Fig. 4. Checking wheel alignment
Toe-in at normal tire pressure should be such that A (Fig. 4), measured along the center line of the side tire surface at the front, was 1.5-3.0 mm undersized B at the rear.
Tighten the lock nuts after adjustment is complete. Tightening torque 103–127 Nm (10.5–13 kgf m).
Wheel alignment can be checked with a model 2182 GARO ruler.
To carry out repairs, remove the front drive axle from the vehicle and disassemble it.
After disassembling and washing the parts, check their condition and determine their suitability for further work.
Repair the crankcase, main gear and differential in accordance with the instructions set out in the article "Dismantling and flaw detection of the rear axle UAZ-3151”.
When and when bending the axle shaft cover, edit it in a cold state.
Replace worn parts of steering knuckles with new ones.
Remove the front axle in the following order:
- 1. Install the pads under the rear wheels of the car.
- 2. Disconnect the hydraulic brake lines on the left and right side members from the flexible hose going to the front wheel brakes.
Remove the nuts securing the flexible hoses and remove them.
- 3. Remove the nuts securing the lower ends of the shock absorbers.
- 4. Remove the bolts securing the front propeller shaft to the drive gear flange.
- 5. Unpin and unscrew the bipod ball stud nut, disconnecting the rod from the bipod.
- 6. Unscrew the nuts securing the front spring ladders, remove the pads, ladders and pads.
Raise the front of the car by the frame.
When removing the spring suspension bridge, follow steps 1-5.
Next, disconnect the anti-roll bar from the trailing arms 1, tie rod 2 from bracket 11 on the frame, the rear ends of the trailing arms 1 from the brackets 5 on the frame.
Dismantling the front axle
Disassemble the front axle in the following order:
- 1. Install the axle on the stand, unscrew the wheel nuts and remove the wheels.
- 2. Unpin and unscrew the nut securing the bipod link pin to the steering knuckle arm and remove the bipod link.
- 3. Loosen the screws and remove the brake drums.
- 4. Remove the wheel release clutches.
- 5. Straighten the bent edges of the lock washer, unscrew the nut and locknut, remove the lock washer and the inner ring with rollers of the outer bearing of the right and left wheel hubs.
- 6. Remove the wheel hubs.
- 7. Unscrew the bolts securing the brake shields, remove the shields, the pivots of the steering knuckles and remove the hinges of the steering knuckles.
- 8. Unpin and unscrew the pin nuts and remove the steering link rod.
- 9. Remove the bolts securing the ball joint to the axle housing.
Remove the wheel swivel stops and press the ball joints out of the axle housings.
- 10. Loosen the nuts securing the swing arm to the steering knuckle housing.
Remove the lever and shim set.
- 11. Unscrew the bolts securing the upper lining of the kingpin of the other steering knuckle and remove the lining with a set of shims.
- 12. Unscrew the bolts securing the lower pads of the pivots and remove the pads with a set of shims.
- 13. Remove the ball joint seal bolts and remove the ball joint seal.
Fig. 5. Pivot puller
- 14. Press out the pins using the tool shown in fig. 5, and remove the steering knuckle housing.
Dismantle the steering knuckle without removing the front axle from the car in the following order:
- 1. Place blocks under the rear wheels of the car.
- 2. Jack up the front wheel on the side to be disassembled.
- 3. Follow the steps 2-10 above in this chapter.
- 4. Unscrew the nuts securing the swing arm or the bolts securing the upper kingpin pad on the body and remove the lever or pad with a set of shims.
- 5. Unscrew the bolts securing the lower kingpin pad and remove the pad with a set of shims.
- 6. Loosen the bolts securing the ball joint oil seal.
- 7. Press the pins with a tool and remove the steering knuckle housing.
Disassembly and assembly of constant velocity joints
Disassemble the hinges in the following order:
- 1. Mark with paint the relative position of the knuckles of the hinges.
- 2. Spread your fists, to do this, tap the fork of a short fist on a wooden stand.
- 3. Clamp the joint by the long fist in a vise with the short fist up.
Fig. 6. Dismantling the hinge
- 4. Turn the short fist towards one of the leading (peripheral) balls.
If the opposite ball does not come out of the grooves, press or hit with a copper hammer (Fig. 6) on the short fist. When doing this, be careful, as one of the balls can fly out of the hinge at high speed.
- 5. Remove the rest of the hinge balls. After selecting new balls of increased sizeera (repair) or replacement of one of the knuckles, assemble the joint.
Assemble the hinges in the following order:
- 1. Clamp your long fist in a vertical position.
- 2. Insert the center bead.
- 3. Place a short fist on the central ball so that the marks marked with paint coincide and, turning it from side to side, install three leading (peripheral) balls in turn.
- 4. Spread the fists by 10-12 mm and rotate the short fist to the maximum angle away from the free grooves, install the fourth ball into the grooves.
- 5. Rotate the short fist to a vertical position. The tension on the hinge balls should be such that the moment required to rotate the fist 10–15 ° in all directions from the vertical with the other fist clamped in a vise is 30–60 Nm (300–600 kgf cm).
The difference in the moments of rotation of the fist in two mutually perpendicular directions of one hinge should not exceed 9.8 Nm (100 kgf cm).
The balls must be sorted into 9 groups to obtain the required tightness and ensure proper assembly.
Dimensions of the diameters of the drive balls of the constant velocity joint in mm:
- First - 25.32–25.34
- Second - 25.34–25.36
- Third - 25.36–25.38
- Fourth - 25.38–25.40
- Fifth - 25.40–25.42
- Sixth - 25.42–25.44
- Seventh - 25.44–25.46
- Eighth - 25.46–25.48
- Ninth - 25.48–25.50
Central ball diameter 26.988-0.05 mm. Each joint must be assembled with balls of one group or two adjacent groups.
For example: two balls with a diameter of 25.41 mm and two balls with a diameter of 25.43 mm.
When assembling balls of the same size, be sure to place diametrically opposite one another.
The difference in the diameters of two pairs of balls of one hinge is allowed no more than 0.04 mm.
After assembly, run the hinge on the stand for 2 minutes at a speed of 4.8 s–1 (300 min -1) with a change in angle from 0 to 30°.
When running in, lubricate the balls and grooves according to the lubrication table.
Front axle assembly
Assemble the front axle in the reverse order of disassembly, taking into account the following:
Press the bushing into the steering knuckle flush with the end face of the socket under the thrust washer.
After pressing the sleeve, unfold and iron with a brooch to a diameter of 32 +0.34+0.17 mm.
Limit the longitudinal movements of the constant velocity joint with thrust washers, one of which is installed in the ball joint, and the other in the trunnion.
Fig. 7. Installing the thrust washer
The oil grooves of the thrust washers must face the pivot.
To secure the washer in the socket, punch it in 3-4 points evenly spaced around the circumference.
The dimension from the plane of the thrust washer 1 (Fig. 7) to the flange of the trunnion 2 should be 7 +0.08 –0.26 mm, from the plane of the washer 1 to the center of the ball bearing 3 - 48.2+0.38 mm.
When replacing bushings of 4 pins in the ball joint, turn them after pressing in to a diameter of 25 +0.030 +0.008 mm. The 24.995 mm diameter gauge must fit into both bushings at the same time.
When installing the ball joint, fill the ball joint with grease according to the lubrication table.
Lubricate the pivots and pivot bushings with liquid lubricant before assembly.
Fig. 8. Selection of shims
The number of spacers to obtain certain axial interference in the pivot bushings, select depending on the size Б (Fig. 8), consisting of the sum sizes of the steering knuckle and shims, and the size A, consisting of the sum of the sizes of the ball joint, support washers and pivots.
The number of pads must be at least five. Measure under a load of 1.6 kN (160 kgf).
The size of А must be 0.02-0.10 mm larger than the size of B.
Install shims from above and below on the ends of the steering knuckle housing.
If there is an even number of spacers of the same thickness, install the latter on top and bottom in equal quantities.
With an even number of spacers but different thicknesses, or with an odd number of spacers, the difference between the total thickness of the upper and lower spacers should not exceed 0.1 mm.
When assembling and installing the ball seal soak its inner felt ring in warm engine oil.
After assembly, check the front axle on the stand with and without load. The load is created by simultaneously braking both axle shafts.
A properly assembled front axle should not have increased noise and heat, as well as oil leakage through cuffs and seals, covers and bolted connections.