Transmission system

INTRODUCTION

• Mechanism that transmits the power from the engine crankshaft to the rear wheels

• Gear box (manual transmission)

• Automatic transmission

Functions of transmission

• To provide a means to vary the torque ratio between the engine and the road wheels as required.

• Provides a neutral position so that the engine and the road wheels are disconnected even with the clutch in the engaged position.

• Provides means to back the car by reversing the direction of rotation of the drive

Location

Types of transmission

• Manual transmission (gear box)– Sliding mesh type gear box– Constant mesh gear box– Synchromesh type gear box

• Automatic transmission

Sliding mesh type of gear box

• Simplest type of gear box

• All the gears on the lay shaft are fixed to it

• Three direct and one reverse speeds are attained on suitably moving the gear on the main shaft by means of selector mechanism.

Constant mesh gear box

• All gears are in constant mesh with the corresponding gears on the layshaft.

• The gears on the main shaft are free.• The dog clutches are provided which are free to

slide on the main shaft.• The gears on the layshaft are fixed.• Weakness: Double declutching(for smooth engagement of the dog clutches it is necessary that the

speed of mainshaft gear and the sliding dog must be equal)

Synchromesh gear box

• Used for smooth meshing• Works like a friction clutch

Advantage

• In constant mesh gear box, the dog clutches connect the gears of the main shaft. This produces noise and jerk. To avoid this the synchromesh gear box is used.