Reason of synchromesh gear box preferred over constant mesh gearbox

1) No need of double declutching as in case of constant mesh gearbox.

2) Smooth engagement of higher gears due to synchromesh device.

3) Less noisy as helical gears are used.

4) Less vibration.

Application of synchromesh gearbox

Modern cars, Sport utility vehicles, for Higher gears in gearbox

Application Synchronizer to avoid double declutching

The main purpose of this unit is to synchronize the speed of the two gears before they are engaged. We know that in running vehicle, when we press the clutch & put the gear in neutral position, till the gear are revoling. All the gear do not revolve at the same speeds & when we have to engage two gears running at different speeds by shift lever there will be some sound due to clashes of gears and very hard to engage and disengage the gears. To avoid said problems the synchromesh devices are used. Synchromesh devices are not fitted to all the gears. They are fitted only on the higher gears. During synchronization the synchronizer sleeve is moved towards selected gear pushing the block ring to the right, the ring contacts the shoulder of the driven gear and begins to synchronize the speed of the two parts. In this way the drive from lay shaft gears to main shaft gear and then to the main shaft through synchronizer device.