-In constantmesh gearbox all the gears on the mainshaft are constantly mesh with layshaft gear & freely rotate on mainshaft.

-When the clutch is in engaed position & gears are netral position & engine is running an additional part called “Dog clutch”is provide between mainshaft gears slide on splined shftb with help of selector mechanism.

-a whole assembly enclosed in the gearbox hausing and filled with specific grade oil in specific quantity

Working:-

Neutral Gear:-in neutral stage all dog clutches remains at centre position and no power transmit throgh gearbox.

1st Gear:- As the right side dog clutch slide towards left and its teeth mesh with teeth of first gear on mainshft than first gear ratio obtained which is near about 3:1

2nd Gear:- When left side dog clutch slide towards right side and its teeth mesh with teeth of second gear on mainshft than second gear ratio obtained which is near about 2.5:1

3rd Gear or Top gear:- When left side dog clutch slide towards left side and its teeth mesh with teeth of clutch shaft gear than third gear ratio obtained which is near about 1:1

Reverse Gear:- As the right side dog clutch slide towards right side and its teeth mesh with teeth of reverse gear on mainshft than direction of mainshaft becomes reverse & reverse gear ratio obtained which is near about 3:1