1. Manual Transmissions

2. Sliding Gear Transmission
Old school, used from late 1800’s to 1940’s?
Has two or more shafts in parallel with sliding spur gears.

3. Sliding Gear Transmission
If either gear is rotating, shifting is difficult and gear “clashing” will result.
Some manufacturers may still have a sliding gear for reverse.

4. Collar-shift Transmission
Has two parallel shafts with gears in constant mesh
These “collars” slide on a hub that is splined to the output shaft, thus transferring power.
Gear “clashing” will occur if the gear speeds are not matched by double clutching.

5. Double Clutching
The shifter, rather than going straight to the next gear, makes a stop in neutral and then the clutch is released.
This is to allow the engine to slow down (or with a tap on the gas, speed up when downshifting) so the transition into the next gear is much more smooth.
The driver then depresses the clutch again and completes the shift into the target gear, and finally the clutch is released again, putting the car back into gear.

6. Synchromesh Transmissions

7. Synchromesh Transmissions
Gears are in constant mesh and are collar shifted
All forward gears are of a helical design

8. Synchromesh Transmissions
Collars are equipped with synchronizers
Synchronizers eliminate the need to equalize gear speeds before engagement
Used on all current models of cars – may use a spur gear for reverse

9. Synchromesh Transmissions
Engine torque is applied to the input shaft (clutch shaft) when the clutch is engaged.
The input shaft is fitted with a gear (input gear or clutch gear)

10. Synchromesh Transmissions
The front of the output shaft is machined to accept a bearing that fits into the input-shaft.
The different speed gears (1st, 2nd, 3rd 4th, etc.) rotate on the main shaft.

11. Synchromesh Transmissions
Parallel to (below or beside) the input and output main shaft is the counter shaft
The counter shaft is fitted with different sized gears.

12. Synchromesh Transmissions
All of these gears are in constant mesh with the gears on the output shaft except …
One gear is in constant mesh with the input shaft gear.

13. Synchromesh Transmissions
Gear changes occur when the selected gear is connected to the output shaft.
This is accomplished by locking a collar onto the selected gear.
The collars are moved by shift forks.

14. Synchronizers
Bring components that are rotating at different speeds to one synchronized speed
The four types of synchronizers are:
Block (most common type used today)
Disc and plate
Plain
Pin

15. Block Synchronizer Assembly
Hub
Sleeve
Blocking ring
Inserts or spring-and-ball detent devices

16. Synchronizer Hub The hub is is internally splined to the mainshaft
The inserts slide back and forth in slots on the hub.
Some inserts use a ridge to detent the slide with an internal groove on the sleeve.

17. Synchronizer Insert
Other inserts are of a ball and spring design

18. Synchronizer Sleeve The sleeve surrounds the synchronizer assembly
Internal splines mesh with the outside splines of the hub
The sleeve is internally grooved perpendicular to the splines to catch the ridge of the insert

19. Synchronizer Sleeve

20. Synchronizer Sleeve
The outside of the sleeve is also grooved to accept the shift fork

21. Blocking Rings
Bronze or brass blocking rings are found at the front and rear of the synchronizer assembly.

22. Blocking Rings …are notched to accept the insert keys on the hub.
Thus the blocking ring and hub turn at the same speed.

23. Blocking Rings
Beveled dog teeth are found on the driven gear and the blocking ring. These are used for alignment during shifting.
The inside of the blocking ring is shaped like a cone to mate with the conical shoulder of the driven gear.

24. Blocking Rings
The inside of the blocking ring’s surface contains sharp grooves.
These grooves disperse oil to maximize friction between the ring and gear.

25. Synchronizer Operation

26. Synchronizer Operation
First, the sleeve is moved toward the gear by the shift lever and engages the hub assembly
Second, the movement of the sleeve causes the inserts to press the blocking ring onto the cone of the gear

27. Synchronizer Operation
Third, when the components reach the same speed, the synchronizer sleeve slides over external dog teeth on the blocking ring and over the dog teeth of the speed gear’s shoulder. This action locks the gear to the main shaft.

28. Advanced Synchronizer Designs
New materials are being introduced for blocking rings including powdered and organic materials.
Manufactures are also using double and triple cone designs to maximize friction and reduce wear.

29. Transmission Types

30. Transmission Types Three-speed transmission
Third gear is direct drive (1:1 ratio)
They are rarely used today
Four-speed transmission
Fourth gear is direct drive (1:1 ratio)
The additional speed ratio is usually between first and second gear
A third hub and sleeve assembly is added to provide for reverse

31. Transmission Types Five-speed transmission
a four-speed transmission with an overdrive
helps increase fuel mileage and engine life
Six-speed
Found on performance cars

32. Transmission Types Overdrive units:
Popular before advent of four-, five-, and six-speed transmissions

33. Gear Ratios

34. Transmission Components
External

35. Transmission Components
Input Shaft

36. Counter Shaft

37. Main Shaft

38. Reverse Idler Gear

39. Fork and Rail Assembly

40. Transmission Operation
Power flow in neutral
The input shaft drives the counter shaft
All of the gears on main shaft rotate
The synchronizers are not engaged with any gear
No power is transferred to the output shaft

41. Power flow in first gear
The power enters the transmission through the input shaft
The first/second synchronizer sleeve is engaged with the first gear dog teeth
The power is transferred from the input shaft, through the countershaft, and up to the first gear
The first gear drives the output shaft

42. Power flow in second gear
The power enters the transmission through the input shaft
The first/second synchronizer sleeve is engaged with the second gear dog teeth
The power is transferred from the input shaft, through the countershaft, and up to the second gear
The second gear drives the output shaft

43. Power flow in third gear
The power enters the transmission through the input shaft
The third/fourth synchronizer sleeve is engaged with the third gear dog teeth
The power is transferred from the input shaft, through the countershaft, and up to the third gear
The third gear drives the output shaft

44. Power flow in fourth gear
The power enters the transmission through the input shaft
The third/fourth synchronizer sleeve is engaged with the fourth gear dog teeth
The power is transferred from the input shaft to the fourth gear
The fourth gear drives the output shaft

45. Power flow in fifth gear
The power enters the transmission through the input shaft
The fifth gear synchronizer sleeve is engaged with the fifth gear dog teeth
The power is transferred from the input shaft, through the countershaft, and up to the fifth gear
The fifth gear drives the output shaft in overdrive

46. Power flow in reverse gear
The power enters the transmission through the input shaft
The reverse gear synchronizer sleeve is engaged with the reverse gear dog teeth
The power is transferred from the input shaft, through the countershaft, through the reverse idler gear, and up to the reverse gear
The reverse gear drives the output shaft in reverse

47. Typical Bearing Locations

48. Transaxles