The gearbox (Fig. 1) has four gears forward and one reverse

The gearbox uses constant mesh gears in second, third and fourth gears

In the third and fourth gears, an inertial type synchronizer is installed, consisting of a sliding clutch, a hub. two blocking tracks and three crackers pressed against the clutch by two spring rings.

To increase rigidity and improve the accuracy of the gear rims, the intermediate shaft is made one-piece in the form of a block of four gears.

Furthermore, for smooth meshing and quiet operation of the gearbox, the gears of constant meshing are made with helical teeth.

Disassembling the gearbox of GAZ-66, GAZ-66-02, GAZ-53.

The gearboxes of the GAZ-66 and GAZ-66-02 cars differ from the gearboxes of the GAZ-53A car in the rear cover device (there are no speedometer drive gears that are installed in the transfer case).

In addition, the gearbox housing of the GAZ-66-02 car has a more accurate tolerance for the size from the axis of the gear block of the intermediate shaft to the mating plane of the hatch on which the power take-off is installed.

Gearbox maintenance

Maintenance of the gearbox consists of checking the mounting, maintaining the required level of lubrication and periodically changing the oil in the crankcase.

Transmission malfunctions and solutions

- Causes of malfunction


  • Gearbox noise:

- Weak fixing bolts

Tighten the bolts

- Wear or damage to parts

Disassemble the gearbox and replace worn parts

  • Noise when shifting gears:

- The cause of this defect is a malfunction of the synchronizer as a result of thread wear on the conical surfaces of the blocking rings and the disappearance of the gap between the ends of the blocking ring and the spur ring of the corresponding gear

Check the gap with a feeler gauge, to do this, remove the top cover of the box and press the locking ring with a clutch against the gear cone. If the gap is less than 0.3 mm, the blocking rings should be replaced with new ones

  • Difficult shifting:

- Incorrect adjustment of the clutch or clutch pedal travel

Adjust clutch and drive

- Seizure in the gearbox drive due to bending or wear of the drive parts

Inspect drive parts and replace defective parts

- Wear of gear mechanism parts

Replace worn parts

- Seizure in the sliding splined joints of the coupling with the synchronizer hub and the driven shaft with the first gear and reverse gear

Replace defective parts

- Gear sticking due to frequent shifting of the gearbox from higher gears to lower gears

Note. Due to the frequent and noisy shifting from second gear to first gear, the ends of the teeth can wear out prematurely, and lead to difficult engagement in first gear.

Replace defective parts

  • Self disengagement of gears while driving:

- Incorrect gear engagement: when the gear is engaged, the clutch pedal is released before the gear is fully engaged

Generate properly

  • - Misalignment of gear teeth due to wear of the following parts:
  • - switching forks;
  • - synchronizer clutch and gears for engaging the first reverse gear;
  • -grooves for the forks on the synchronizer clutch and gears for engaging the first gear and reverse gear;
  • - bearings of the driving, driven and intermediate shafts and their retaining rings

Replace worn parts

- Strong wear of the forks and shift rods, as well as loosening of the fastening of the forks on the rods

Replace worn stems and forks, ensuring the required fastening of the forks on the stems

- Weak tightening of the nuts securing the gearbox and driven shaft. If the driven shaft has axial movement, then this can lead to self-deactivation of gears

Tighten nuts

  • Gearbox oil leak:

- Weak tightening of the top cover bolts (oil leakage between the cover and the crankcase)

Tighten the bolts

- Damage to bearing caps and their gaskets

Replace worn parts

- Unsatisfactory work of the breather (sticking it with dirt)

Clean the breather from dirt or replace it with a new one

- Formation of cracks in the crankcase and top cover

em>Replace parts with cracks

- Oil seal wear

Replace oil seal

  • Drive shaft bearing damage:

- Cardan shaft imbalance

Check the balance of the cardan shaft, the condition of the cardan shafts and the bearing of the intermediate support on the GAZ-53A car

  • Drive shaft bearing failure:

- Weak tightening of the bearing cap bolts

Tighten the cover bolts

- Incorrect assembly of the gearbox and clutch

Correctly assemble the gearbox and clutch

Gearbox Repair

  • Removing the gearbox from the vehicle.

To remove the gearbox from a GAZ-53A car, you need:

  1. - put the car on the inspection ditch;
  2. - remove the rubber floor mat and the rubber sealing cap of the upper cover of the gearbox;
  3. - remove the gearbox control lever, for which, while pressing the lever down, turn the fixing cap of the top cover counterclockwise;
  4. - close the hole for the lever with a wooden plug;
  5. - remove cover;
  6. - drain oil;
  7. - disconnect the rear end of the hand brake link;
  8. - disconnect the hand brake lever assembly from the top cover of the box;
  9. - disconnect the clutch release rod;
  10. - remove the return spring and the clutch release fork;
  11. - unscrew the cap oiler of the clutch release clutch bearing;
  12. - remove the ventilation hatch of the clutch housing;
  13. - unscrew the bolts securing the cardan shaft to the flange of the driven shaft of the gearbox;
  14. - unscrew the bolts of the intermediate support of the cardan shaft and, without disconnecting the cardan shaft from the flange of the drive gear shaft of the final drive, take it to the side;
  15. - remove the central brake drum (if the box is dismantled without removing the exhaust pipes of the muffler);
  16. - disconnect the speedometer drive cable from the gearbox;
  17. - fix the chain of the lifting device with two bolts securing the upper cover of the gearbox, disconnect the gearbox from the clutch housing, use the tool to move it back and lower it down.

Removal of the gearbox and power take-off from the GAZ-66-02 car must be performed in the following sequence:

  • 1. Raise cab.
  • 2. Unscrew the bolts securing the cab cross member (on the left side of the vehicle) to the frame.
  • 3. Disconnect the manual throttle link from the lever.
  • 4. Disconnect the choke control rod from the carburetor.
  • 5. Disconnect the brake control cable from the sunblind lever.
  • 6. Disconnect the blind control cable from the frame.
  • 7. Loosen the bracket of the left fuel tank fuel line from the cab cross member and release the fuel line.
  • 8. Disconnect the starting heater wires from the heater motor, solenoid valve and heater glow plug.
  • 9. Disconnect the handbrake vertical link from the lever.
  • 10. Remove the transfer case lever handles.
  • 11. Disconnect the fuel system pipes from the fuel tank changeover valve.
  • 12. Remove the faucet guard.
  • 13. Disconnect the vacuum brake booster shut-off valve from the floor.
  • 14. Loosen the bracket of the left fuel tank fuel line from the cab cross member and release the fuel line.
  • 15. Remove the cover of the starting heater control panel. Disconnect the wire from the push-button fuse of the starting heater.
  • 16. Disconnect the wire terminal from the mass switch.
  • 17. Disconnect the rubber tube from the brake booster breather.
  • 18. Disconnect the pipe from the tire pressure control valve.
  • 19. Remove the power take-off lever handle.
  • 20. Remove the protective cap of the gear lever and remove the lever.
  • 21. Disconnect the front end of the intermediate driveshaft.
  • 22. Remove the polik together with the cab cross member.
  • 23. Remove the transfer box lever mounting bracket.
  • 24. Remove the clutch fork spring.
  • 25. Unscrew the clutch release bearing oiler.
  • 26. Remove the clutch housing vent cover.
  • 27. Remove the clutch fork.
  • 28. Remove gearbox with power take-off.

Gearbox Disassembly

Removing the center brake.

  • 1. Remove the top cover assembly.
  • 2. Remove the assembled clutch with the central brake drum from the driven shaft.
  • 3. Remove the drum from the clutch.
  • 4. Remove in sequence: oil deflector, oil deflector gasket, center brake assembly, center brake disc deflector.
  • 5. Remove lever from center brake lever pin. Remove the fitting and driven gear of the speedometer drive from the rear cover, then unscrew the breather.
  • 6. Remove the rear cover and speedometer drive gear.
  • 7. Remove the driveshaft cover.

dismantling the drive shaft from the gearbox GAZ-66, GAZ-53

  • 8. Turn the drive shaft so that the semicircular recess on its spur ring and on the cone is at the bottom, then remove the assembled drive shaft from the crankcase (Fig. 2)
  • 9. Remove the ball bearing circlip.
  • 10. Remove gasket and power take-off hatch cover.

dismantling the intermediate shaft from the GAZ-66 gearbox

  • 11. Remove the intermediate shaft rear cover and reverse axle thrust plate.
  • 12. Remove the ball bearing of the intermediate shaft, having previously pulled the shaft out of the crankcase (Fig. 3 and 4).

Removing the GAZ-66 intermediate shaft bearing

  • 13. Remove intermediate shaft with inner ring assembly from crankcase. Remove the roller bearing inner race from the intermediate shaft.
  • 14. Remove the intermediate shaft roller bearing outer race from the crankcase. When disassembling and assembling the gearbox, it should be noted that the outer and inner rings of this bearing are not interchangeable. Therefore, if it is necessary to replace one of the rings, the entire bearing must be replaced.
  • 15. Remove the shaft of the reverse gear set.
  • 16. Remove the reverse gear assembly from the crankcase.
  • 17. Remove the intermediate shaft front bearing plug.
  • 18. Remove the dirt trap from the crankcase.

Drive Shaft Disassembly

Remove the retaining ring, remove the thrust washer and the rollers of the front bearing of the output shaft.

On parts of cars, the retaining ring and thrust washer are not installed.

The rollers of the front bearing of the output shaft are not interchangeable.

They are sorted into groups at intervals of 0.005 mm and put into the assembly as a set from only one group, so when one or more rollers are worn out, the entire set needs to be replaced.

Remove and unscrew the ball bearing nut and remove the bearing.

Disassembly of the output shaft

Removing the hub and synchronizer sleeve

Remove the first gear and reverse gear from the shaft.

Remove and unscrew the nut securing the synchronizer hub.

Remove the hub and sliding sleeve of the synchronizer (fig. 5).

Remove crackers and synchronizer springs.

Remove in sequence: synchronizer ring, third gear, spacer, thrust washer, second gear

GAZ-66, GAZ-53 gearbox synchronizer

Top Cover Disassembly

  • 1. Remove the plug from the hole for the locking plunger.
  • 2. Remove two pins from the neck of the cap.
  • 3. Remove the conical spring.
  • 4. Knock out the stoppers from the shift fork and the transfer head of the first and second gear rod.
  • 5. Remove the fork and decal from the shift shaft of the first and second gears and remove the stem.
  • 6. Knock out the stop of the shift fork of the third and fourth gears.
  • 7. Remove the shift fork of the third and fourth gears from the stem, remove the stem and remove the locking pin from it.
  • 8. Knock out the locking pins from the fork and the reverse gear head. Remove the fork and decal assembly from the reverse shift rod and remove the rod.
  • 9. Remove the retaining springs, plungers and stem retainer balls from the holes in the cover.

Top cover with gearbox control mechanism GAZ-66

Disassembly of the reverse rod decal. Undo and unscrew the spring retainer.

Remove the spring and fuse.

Definition of technical condition

Details of the disassembled gearbox (except for the bearings) soak in a cleaning solution and then rinse.

In parts with oil channels, thoroughly clean the latter.

After washing, carefully inspect the parts. replace parts with cracks.

If there are nicks, burrs, or other irregularities on the machined surfaces, smooth out these irregularities to ensure a good fit of the mating parts.

In this case, special attention should be paid to the condition and geometry of the seating surfaces for bearings in the crankcase and on the shafts.

Carefully check the condition of the gearbox gear teeth.

On the working surface of the tooth, on an area of ​​​​no more than 10% of the entire surface, small shells (pitting) are allowed. Clean minor nicks, burrs on the ends of the teeth.

Chips on the work surface are not allowed. Inspect the condition of the splines in the splines and the grooves for the shift forks.

If there are scoring, heavy wear, crushing or chipping in the fork grooves and splines, the parts must be replaced.

Replacement is also subject to parts with stripped threads, as well as the development of the surface under the stuffing box.

Wash the bearings in a clean solution and wipe with a cloth or blow with compressed air.

If the bearings are suitable for further work, then after drying them, lubricate them with the lubricant that is used for the gearbox and store until they are needed.

Rejection signs of bearings are:

- cracks, chips, risks and spalling of metal on balls (or rollers) and on raceways, increased radial clearance.

The allowable radial clearance is:

  • -0.05 mm for ball bearings;
  • - 0.08 mm for the intermediate shaft roller bearing.

The amount of radial clearance in ball bearings is determined as follows:

The bearing is installed so that its axis is horizontal. The ends of one of the rings, for example, the outer one, are fixed motionless.

After that, the free inner ring is moved in the radial direction under a load of 10 kg.

In this case, the maximum radial clearance will appear in the upper part of the bearing between the ball and the surface of the raceway.

To determine the gap, move the inner ring under the specified force in the opposite radial direction and measure the amount of movement with an indicator.

In this way, you can determine the radial clearance in the roller bearing of the intermediate shaft.

At the gearbox housing, the holes for the bearings of the drive and driven shafts, as well as for the bearings of the intermediate shaft, must be bored from one installation.

The distance from the axis of the holes for the bearings of the drive and driven shafts to the axis of the holes for the bearings of the intermediate shaft must be within 110.625 ± 0.07 mm.

The axis of the holes for the intermediate shaft bearings must be parallel to the axis of the holes for the bearings of the drive and driven shafts and lie in the same plane with it, the deviation should not exceed 0.04 mm over a length of 250 mm.

The distance from the axis of the holes for the intermediate shaft bearings to the axis of the holes for the axis of the reverse gear unit must be within 71.25 ± 0.07 mm.

The axis of the holes for the axis of the reverse gear unit must be parallel to the axis of the holes for the bearings of the drive and driven shafts and must lie with them in the same plane.

The deviation should not exceed 0.08 mm over a length of 200 mm.

The front and rear end planes of the crankcase must be perpendicular to the axis of the holes for the bearings of the drive and driven shafts. The deviation should not exceed 0.07 mm at a radius of 75 mm.

The inner ends of the eye for the reverse gear unit must be perpendicular to the axis of the holes for the axis of the reverse gear unit. The deviation should not exceed 0.1 mm at a radius of 21 mm.

Burrs and nicks on gear teeth must be cleaned.

After assembling the synchronizer (when replacing the conical rings), it is necessary to process the conical surfaces of the rings so that the gap between the ends of the ring and the gear after grinding in the cones is within 0.8 - 1.25 mm.

The lapping surface area must be at least 70% of the cone surface. Check according to the standard.

The gears of the gearbox should be selected so that the backlash between the teeth is within 0.3 - 0.4 mm.

The gear of the 1st gear must be selected to the driven shaft so that the side clearance between the splines is no more than 0.18 mm.

Clutch, sliding shifting of 3rd and 4th gears must be selected with a hub.

At the same time, easy movement of parts without noticeable side clearance should be ensured.

In the extreme positions of the sliding clutch of the 3rd and 4th gears, corresponding to the 3rd and 4th gears, the longitudinal movement of the clutch is allowed within 0.2 mm.