4-Speed Manual Gearbox

The gearbox is designed specifically for front-wheel drive cars, with all shafts, gearwheels, differential and inner universal joints forming an integral unit.

All forward gears are synchromesh, whereas reverse is engaged by means of a sliding gear. The shafts are journalled in the gearcase in ball bearings and taper roller bearings. The output shaft gearwheels are journal led in bushes. All gearwheels except reverse are permanently in mesh and have helical teeth.

The front part of the transmission assembly consists of a primary drive, driven by the engine through the clutch and transmitting the engine output to the gearbox itself. The gearbox is located under the engine, and part of the gearcase serves as the engine oil sump.

The operation of the transmission system is illustrated by the diagrammatic arrangement. The engine output is transmitted through the clutch and primary chain drive to the gearbox input shaft. In 1st gear, power is transmitted through the layshaft pinion to the output shaft through the gearwheel for 1st gear which is journalled on the output shaft and is locked to the shaft by a sliding sleeve.

In 2nd and 3rd gears, power is transmitted to the output shaft in a similar manner, the gearwheels for 2nd and 3rd gearwheels being locked to the output shaft by corresponding sleeves. In top gear, the input shaft is locked to the output shaft by means of a sleeve, and power is thus not transmitted through the layshaft.





4-SPEED TRANSMISSION ASSEMBLY





SCHEMATIC ARRANGEMENT OF THE 4-SPEED TRANSMISSION SYSTEM
1. Clutch shaft
2. Primary chain drive
3. Layshaft pinion set
4. Reverse gear
5. Reverse gear shaft
6. Output shaft
7. Differential housing

Reverse gear consists of an extra shaft and a gear journalled on it. This gear is in constant mesh with 1st pinion on the layshaft. The reverse gear can be engaged into mesh with a gearwheel on the output shaft. This gearwheel is located behind 1st gear on the output shaft. When reverse gear is engaged, power is thus transmitted from the layshaft pinion to the reverse gear and then to the gearwheel on the output shaft. This arrangement reverses the direction of rotation of the output shaft.

The gearbox is equipped with a reverse gear brake which provides smoother engagement of reverse gear. The brake consists of a spring mounted on the selector rod. As reverse gear is engaged, the spring applies a light pressure to the 1st/2nd selector fork, thus braking the gears by means of the 1st gear synchromesh mechanism.





REVERSE GEAR BRAKE