Manual Transmission Operation

OPERATION OF TRANSMISSIONS

Each manual transmission uses the same method to control the gears, but the construction will vary from model to model. The control lever may be mounted in the top of the cover and come up through the floor of the vehicle cab, or the lever may be mounted under the steering wheel on the steering column.

Tactical military wheeled vehicles use the top cover mounted control lever. Inside the transmission the shift control parts may be mounted in the top of the transmission case or in the cover assembly.

Most military vehicles have the shift mechanism mounted in the transmission cover. This method of construction provides easier repair and disassembly.

Two or more shifter shafts are placed in drilled passages in the cover and are in line with the main shaft. The shifter shafts can move forward, backward, or stay in the center-neutral position. With three positions, each shifter shaft can provide two transmission speeds along with the center-neutral position. Most three-speed-forward transmissions will have two shifter shafts in the control mechanism. Larger transmissions with more speeds must have additional shifter shafts.

To hold the shifter shaft in position, poppet balls and springs are mounted in passages drilled at right angle to the shifter shafts. The poppet ball spring pushes the steel ball into the detents or recesses in the shifter shaft to prevent movement. Three detents are made into the side of each shifter shaft, thus providing one for each shift position.

Mounted on each shifter shaft at the correct position is a shifter fork, which is held in place by a bolt or pin. The fork extends from the shifter shaft down into the case to fit into a groove made on a sliding gear. At the top of the shifter fork is a slot made to receive the lower end control lever.

The control lever is mounted in the transmission cover with a ball joint, allowing the control lever to be moved forward and backward or right and left. A pin at the ball joint prevents the lever from spinning in a circle. The upper part of the lever is outside of the transmission and extends into the vehicle cab.

Located between the shifter shafts and in line with the poppet balls and springs is an interlock device. The device is usually a ball or pin engaging notches in each shifter shaft and is able to slide sideways between the shifter shafts. This interlock device prevents two speeds from being engaged at the same time.

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Article Pages
1. Drive Train Intro
2. Principles Of Torque
3. Fundamentals Of Gears
4. Types Of Gears
5. Gear Principles
6. Principle Of Gear Ratios
7. Principle Of Torque Ratios
8. Operation Of A Gear Train
9. The Construction And Operation Of A Planetary Gearset
10. Operating Principles Of A Planetary Gearset
11. Why Clutches Are Needed
12. Clutch Construction
13. Types Of Clutches
14. Clutch Operation
15. Clutch Maintenance
16. Introduction To Manual Transmissions
17. Types Of Manual Transmissions
18. Manual Transmission Construction
19. Manual Transmission Operation
20. The Powerflow In Manual Transmissions
21. Manual Transmission Lubrication
22. Manual Transmission Ventilation
23. Constant Mesh Transmissions
24. Synchromesh Transmissions
25. Power Take-Offs
26. Power Take-Offs Construction And Operation
27. Input Gear, Output Shaft and Shifter Fork
28. Inspecting The Transmission
29. Leaking Lubricants In A Manual Transmission
30. Leaking Seals In A Manual Transmission
31. Testing Transmissions For Malfunctions
32. Power Take-Off Inspecting And Testing
33. Automatic Transmission Introduction
34. Automatic Transmission Fundamentals
35. Drive Train Mechanisms
36. Drive Train Operation
37. The Drive Train Arrangements Of The Automatic Transmission
38. Simpson Drive Train
39. Hydraulic System Of The Automatic Transmission
40. Hydraulic Supply System
41. Torque Converter Feed Circuit
42. Range Control System
43. Vehicle Speed Versus Engine Loading
44. Transfer Case
45. Transfer Operation
46. The Construction And Operation Of Sprag Units

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