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Fig. 17: 1. Primary shaft. 2. Secondary shaft. 3. Primary shaft constant mesh pinion. 4. Breather. 5. Fourth gear synchronizer ring gear. 6. Third and fourth gear synchronizer sliding sleeve. 7. Third and fourth gear shift fork. 8. Gearbox housing. 9. Third gear synchronizer ring gear and toothed wheel. 10. Second gear synchronizer ring gear and toothed wheel. 11. First and second gear shift fork. 12. First and second gear synchronizer clutch hub. 13. First and second gear synchronizer sliding sleeve. 14. First gear synchronizer ring gear and toothed wheel. 15. Reverse gear wheel. 16. Gear shift lever. 17. Speedometer drive pinion. 18. Flexible coupling flange. 19. Reverse gear fork. 20. Reverse gear fork rod. 21. Third and fourth gear fork rod. 22. First and second gear fork rod. 23. First and second gear limit screw. 24. Intermediate shaft. 25. Intermediate shaft reverse gear wheel. 26. Reverse gear intermediate gear wheel shaft. 27. Reverse gear intermediate gear. 28. Speedometer drive driven gear. 29. Gearbox rear cover. 30. First gear gear wheel sleeve. 31. First gear gear wheel of intermediate shaft. 32. First gear synchronizer locking ring. 33. Drain plug. 34. Second gear synchronizer locking ring. 35. Intermediate shaft second gear toothed wheel. 36. Intermediate shaft third gear toothed wheel. 37. Third gear synchronizer locking ring. 38. Third and fourth gear synchronizer clutch hub. 39. Fourth gear synchronizer locking ring. 40. Intermediate shaft constant mesh toothed wheel. 41. Clutch housing. 42. Synchronizer locking ring spring. 43. Spring thrust washer. 44. Belleville spring. 45. Synchronizer hub retaining ring. 46. Synchronizer locking ring retaining ring. I - Neutral position. II - Start of third gear engagement. III - Third gear fully engaged.
The principle of operation of the gear transmission is based on changing the engagement of those pairs of gears that participate in the transmission of torque from the primary (driving) shaft 1 to the secondary (driven) shaft 2. This is achieved by moving the sliding clutches 6 and 13 of the synchronizers or the intermediate gear 27 of the reverse gear using the gearshift lever. In this case, the gear ratios of the gears change, and therefore the magnitude of the transmitted torque. In direct fourth gear, the torque transmitted to the driving wheels of the car is almost equal to the torque on the crankshaft of the engine. In first gear, the torque increases by 3.67 times, in second gear by 2.10 times, in third gear by 1.36 times, and when reverse gear is engaged by 3.53 times.
Since 1987, all VAZ vehicles have unified gearboxes in terms of gear ratios and differ from each other in speedometer drives. Each speedometer drive corresponds to its final drive gear ratio. For external differentiation, a paint mark is applied to the speedometer drive: blue for final drive gear ratio 3.9; red for 4.1; not painted for 4.3. Also on the clutch housing (opposite the breather) markings are applied indicating which model it is installed on. For example, for a VAZ-2106 car it is marked with the number 6, for a VAZ-2105 - 5.
The torque transmission diagrams when all gears are engaged are shown by arrows in the figure.
When the gearshift lever is in neutral, no torque is transmitted to the secondary shaft. But since the engine is running and the clutch is engaged, rotation from the primary shaft 1 is transmitted to the intermediate shaft via pinion 3 and constant mesh gear 40. Rotation is transmitted from gears 31, 35 and 36 of the intermediate shaft to gears 14, 10 and 9 of the secondary shaft. Since these gears are not directly connected to shaft 2, they will rotate freely on the secondary shaft. The connection of these wheels to shaft 2 is carried out through synchronizers.
When the first gear is engaged, the force from the gearshift lever is transmitted through the rod and fork 11 to the sliding clutch 13. Moving along the splines of its hub 12, the clutch engages with the straight-toothed crown of the wheel 14. In this way, the synchronizer clutch connects the hub 12 and the wheel 14.
The article is taken from an online resource (VazBook.ru)
And since hub 12 is rigidly connected to shaft 2, the torque from wheel 14 is transmitted through clutch 13 to hub 12 and from it to the secondary shaft of the gearbox. When the second gear is engaged, clutch 13 connects hub 12 to the spur ring of wheel 10, and the torque is transmitted from wheel 10 to hub 12 and to the secondary shaft. Third and fourth gears are engaged by another synchronizer. When third gear is engaged, the torque from primary shaft 1 through wheels 36 and 9 is transmitted through clutch 6 to hub 38 and then to the secondary shaft.
The fourth gear is called direct when the torque is transmitted directly from the primary shaft 1 to the secondary shaft 2, bypassing the gear wheels of the intermediate shaft. In this case, the clutch 6 connects the gear ring 5 of the primary shaft with the hub 38. The rotation frequency of both shafts will be the same, and the magnitude of the torque transmitted from the engine to the drive wheels does not change.
When the reverse gear is engaged, the force from the gear shift lever is transmitted through the rod 20 and the fork 19 to the intermediate gear wheel 27. Moving on the axis 26, it connects the reverse gear wheels 25 and 15, and the torque is transmitted from the primary shaft through the pinion 5 and the gear wheel 40 to the intermediate shaft and then through the gear wheels 25, 27 and 15 to the secondary shaft. In this case, the latter will rotate in the opposite direction, ensuring the reverse rotation of the vehicle's drive wheels.
As can be seen from the gearbox operation diagram, all forward gears are synchronized. The principle of operation of the synchronizer when engaging third gear is shown in diagrams a, b, c. With the gearshift lever in neutral (see diagram a) there is a gap between the sliding clutch 6 and the blocking rings 37. The blocking rings are pressed by springs 42 against the retaining rings 46. In this position, the teeth of the blocking rings are in the depressions of the toothed rims 5 and 9. Due to the gap between the clutch 6 and the blocking rings 37, the torque from the toothed rim 9 is not transmitted through the blocking ring.
At the initial moment of engaging the third gear (see diagram b) sliding clutch 6, moving along the splines of hub 38, is pressed against the conical surface of the blocking ring. Semi-dry friction occurs between the conical surfaces of the clutch and the ring, as a result of which the blocking ring is braked and rotates at a small angle (circumferential stroke from 2.5 to 5 mm). In this case, the side bevels of the teeth of the locking ring rest against the side bevels of the teeth of the ring 9, and further rotation of the locking ring stops. At the same time, resistance is created to further axial movement of the clutch 6. This occurs until the rotation frequencies of the secondary and intermediate shafts of the gearbox are equalized. As soon as this moment occurs, the friction force between the conical surfaces of the clutch and the ring decreases. Under the action of the axial force transmitted from the rod to the sliding clutch of the synchronizer, the locking ring begins to slide along the bevels of the teeth of the ring 9 and, together with the clutch, moves along the teeth of the ring. In this way, the clutch connects the hub 38 and the toothed ring 9. The third gear is fully engaged (see diagram in). In this position, the synchronizer sleeve together with the rod is held by a ball retainer.
Clear and complete engagement and shifting of gears is ensured by the good technical condition of the gearbox itself, as well as the clutch. Sometimes gears shift with some difficulty. This can happen when the gear shift forks are deformed, when the rods or the spherical joint of the lever are jammed, and also when the clutch is not fully disengaged. When the locking rings, teeth of the synchronizer clutches and locks are worn out, spontaneous disengagement or unclear engagement of gears occurs. When the gear wheels, bearings and synchronizers are worn out, noise occurs in the gearbox, and when the seals are worn out or the covers are loosened, oil leaks. The above malfunctions, with proper operation of the car, can occur only with very long-term use of the car.