Assemble the differential in the following order:

  • 1. Before assembling the differential, lubricate the gears of the axle shafts, satellites, thrust washers and the axles of the satellites with gear oil
  • 2. Install the thrust washers on the journals of the gears of the axle shafts.
  • 3. Install the axle gear with thrust washer assembly into the left satellite box.
  • 4. Install the satellites on the axis of the split cross.

Assembling the UAZ-3151 rear axle

Fig. 7. Pressing out the outer ring of the differential bearing

  • 5. Install the split cross (fig. 1) with satellites in the left satellite box.

UAZ-3151 rear axle assembly

Fig. 8. Installing satellite boxes by marks

  • 6. Install the axle gear with thrust washer assembly into the right pinion box.

While holding the axle gear, install the right satellite cup on the left one so that the marks (Fig. 2) (serial numbers) of both cups are aligned.

  • 7. Connect the halves with bolts and tighten them. Tightening torque 32–40 Nm (3.2–4.0 kgf).

 Rear axle

Fig. 20. Rear axle

  • 8. Install the final drive gear to the pinion box, aligning the bolt holes. Install the bolts and tighten them.

Tightening torque 98–137 Nm (10–14 kgfm).

At the assembled differential, the gears of the axle shafts must be rotated using a splined mandrel from a force of not more than 59 N (6 kgf) applied at a radius of 80 mm.

Adjust the differential bearings (if they are replaced) in the following order:

UAZ-3151 rear axle assembly

Fig. 9. Pre-pressing the inner rings of the differential bearings

  • 1. Press the inner rings of the bearings (Fig. 9) of the differential onto the journals of the assembled differential so that there is a gap of 3.5–4.0 mm between the ends of the satellite box and the ends of the inner rings of the bearings.

UAZ-3151 rear axle assembly

Fig. 10. Rolling in differential bearing rollers

  • 2. Install the differential assembly into the crankcase, then the gasket and the crankcase cover and, turning the cover by the casing, roll the bearings so that the rollers are in the correct position (Fig. 10).

Then use bolts and nuts to evenly connect the cover to the crankcase.

UAZ-3151 rear axle assembly

Fig. 11. Clearance measurements when adjusting differential bearings

UAZ-3151 rear axle assembly

Fig. 12. Clearances A and A1 between the ends of the inner rings of the bearings and the satellite box

  • 3. Unscrew the bolts again, carefully remove the cover, remove the differential from the crankcase and measure the gaps A and A1 (Fig. 11 and 12) between the ends of the inner rings of the bearings and the satellite box with a feeler gauge.
  • 4. Choose a package of gaskets with a thickness calculated by the formula:

s = A + A1 + 0.1, where: s is the thickness of the gasket package, mm;

A and A1 - gaps between the ends of the inner rings of the bearings and the satellite box, mm;

0.1 - constant value (to ensure preload), mm.

  • 5. Remove the differential bearing inner races. Divide the selected gasket pack roughly in half.

Install the gaskets on the necks of the satellite box and press the inner races of the bearings up to the stop.

Assemble and adjust the drive gear bearings in the following order:

UAZ-3151 rear axle assembly

Fig. Fig. 13. Piercing of the end face of the shank after pressing the bearing: A - the place of punching

UAZ-3151 rear axle assembly

Fig. 14. Installing the spacer and shims of the drive gear front bearing

  • 1. Press the bearings onto the drive gear. After pressing the rear support bearing with cylindrical rollers, open the end of the shank on which it is pressed (Fig. 13).

Place the spacer (fig. 14) and shims of the front bearing (double-bevel) of the drive gear between the inner rings.

  • 2. Install the adjusting ring 5 (see Fig. 20) of the drive gear 9 (not installed since 1991).

UAZ-3151 rear axle assembly

Fig. 15. Checking the tightness of the drive gear bearings

  • 3. Press the drive gear assembly with bearings into the crankcase until it stops and adjust the preload of the front bearing by changing the thickness of the gasket pack 8 and tightening the nut 7 to failure.

In this case, the oil ring 6 and the flange must be installed on the gear shaft, and the front bearing cover must be removed so that the friction of the cuff on the flange does not affect the measurement readings.

To reduce the tightness, add spacers, to increase, remove.

When properly adjusted, there should be no axial clearance, and the spring dynamometer should show a force of 15–30 N (1.5–3 kgf) for worn-in bearings and 20–35 N (2.0–3.5 kgf) for new bearings when turning the gear by the hole in the flange (Fig. 15).

  • 4. After completing the adjustment, remove the flange, install the gaskets and the cover of the front bearing of the drive gear.

Fix the cover with screws. Install the flange, tighten nut 7 (see Fig. 20) and cotter pin. Tightening torque 167–206 Nm (17–21 kgfm).

Adjust the side clearance and the position of the final drive gears after adjusting the bearings of the drive gear and differential in the following order:

  • 1. Install the differential assembly with adjusted bearings in the crankcase.

Install the gasket on the plane of the crankcase connector with the cover. Install the crankcase cover and secure with bolts.

UAZ-3151 rear axle assembly

Fig. 16. Checking the side clearance in the meshing of the final drive gears

  • 2. Measure the backlash between the teeth of the drive and driven gears, which should be 0.2–0.6 mm.

Measure on the drive gear flange at a radius of 40 mm (Fig. 16).

Regulate the side clearance by moving the spacers 3 (see Fig. 20) from one side of the differential box to the other.

If you remove the spacers from the side of the driven gear, then the gap in the engagement increases, but if you add, the gap decreases.

Replace the spacers without changing their number, as this will violate the differential bearing preload.

Assembling the UAZ-3151 rear axle

Fig. 17. Contact patch of final drive gears

  • 3. On axles with an adjusting ring 5 (see Fig. 20), check the gear engagement along the contact patch.

To do this, paint the teeth of the driven gear with paint.

Keep in mind that very thin paint spreads, and too thick paint does not squeeze out of the gaps between the teeth.

Then, using the axle shafts, slow down the driven gear, and rotate the drive gear in both directions until a clear contact patch is indicated.

In fig. Figure 17 shows typical pinion gear tooth contact positions and how to correct incorrect contact.

Move the drive gear by installing an adjusting ring 5 (see Fig. 20) of a different thickness.

Move the driven gear by rearranging the gaskets of 3 bearings of the differential.

Also carry out the specified check of gear engagement on axles with final drives.

Rear axle assembly

Assemble the rear axle after adjusting the gear engagement in the following order:

UAZ-3151 rear axle assembly

Fig. 18. Measuring the gap between the bearing cover and the crankcase for the selection of gaskets hell

  • 1. Install the shim pack between the end of the drive gear front bearing cap and the crankcase.

The thickness of the package should be 1.3 times the gap (Fig. 18) between the ends of the cover and the crankcase. If necessary, increase the thickness of the package by 1.4 times.

  • 2. Install the drive gear front bearing cap with collar assembly and secure with bolts.
  • 3. Install flange and washer. Tighten nut 7 (see Fig. 20) to the full so that the slots in it coincide with the holes in the gear shank and cotter pin. Tightening torque 167–206 Nm (17–21 kgf m). Do not unscrew the nut to match the groove and the hole for the cotter pin.
  • 4. Install the differential with the driven gear and bearings in the axle housing.
  • 5. Install the gasket between the crankcase and the cover.
  • 6. Install the crankcase cover so that both spring pads are at the top of the axle.

Connect the cover and crankcase with bolts and nuts.

  • 7. Turning the drive gear, check for binding or rubbing in the assembled bridge.

After assembling the bridge, check that it heats up while the vehicle is in motion. If the crankcase becomes very hot (over 90 °C), check the correct bearing adjustment.