Synchronization

General Information

Applies to: 1991–1994; M46

M 46 Transmission

1. X. Neutral position
2. Y. Synchronizing
3. Z. Gear engaged

1. 1. Gear dog teeth
2. 2. Synchro ring
3. 3. Synchro sleeve
4. 4. Dogs
5. 5. Synchro hub
6. 6. Spring
7. 7. Synchro ring
8. 8. Synchro sleeve

A and B are forces caused by different speeds of gear and synchro ring. C is force from synchro sleeve shift fork.

When engaging a gear, a shift fork moves the synchro sleeve (3) towards the gear teeth (1). The synchro dogs (4) move with the sleeve and press the synchro ring against the cone on the gear. If the sleeve and the gear are rotating at different speeds the synchro ring will rotate in relation to the sleeve. The synchro dogs, however, prevent the synchro ring from turning more than half a tooth width. Consequently the synchro sleeve will not be able to slide over the synchro ring and engage the gear teeth.

Since the synchro dogs are pushed up against the synchro ring and the gear cone, friction results between the two surfaces. This friction will equalize the speeds of the gear and synchro sleeve. With both turning at the same speed, the synchro sleeve can then turn the synchro ring half a tooth backwards. The synchro sleeve can then slide over the synchro ring and engage the gear teeth.

Power flow

1st gear

2nd gear

3rd gear

4th gear

Reverse

Overdrive

The overdrive is an additional gear unit between the gearbox and the propeller shaft. It is operated by an electric solenoid controlled by a switch mounted on the gear lever. When the overdrive is in operation the propeller shaft rotates at a higher speed than the gearbox output shaft. Gear ratio is approximately 0.8:1. The propeller shaft and output shaft rotate at the same speed when the overdrive is disengaged.