Working of a Manual transmission is explained in an illustrative and logical manner in this video with the help of animation. Here the working of Sliding mesh and synchromesh transmissions are well illustrated. This video also explains the working of a reverse gear.

Video – Learn Engineering

The gear lever, operated by the driver, is connected to a series of selector rods in the top or side of the gearbox. The selector rods lie parallel with shafts carrying the gears.

The most popular design is the constant-mesh gearbox. It has three shafts: the input shaft, the layshaft and the mainshaft, which run in bearings in the gearbox casing.

There is also a shaft on which the reverse-gear idler pinion rotates.

 The engine drives the input shaft, which drives the layshaft. The layshaft rotates the gears on the mainshaft, but these rotate freely until they are locked by means of the synchromesh device, which is splined to the shaft.

It is the synchromesh device which is actually operated by the driver, through a selector rod with a fork on it which moves the synchromesh to engage the gear.

The baulk ring, a delaying device in the synchromesh, is the final refinement in the modern gearbox. It prevents engagement of a gear until the shaft speeds are synchronised.

On some cars an additional gear, called overdrive, is fitted. It is higher than top gear and so gives economic driving at cruising speeds.