Internal Components

The gearwheels are mounted on three short parallel shafts: the primary shaft (A) and two layshafts (B and C) both in constant mesh with the final drive crownwheel (5). This means there are only two sets of gears transmitting power for each forward gear; even with the three shafts, this gives the same high efficiency as with conventional transverse transmissions.

From the clutch, power from the engine passes to the transmission input
shaft (2) and from there via different combinations of gears (depending on the gear in use) to the final drive (differential), driveshafts and front wheels.

In 1st, 2nd, 3rd and 4th gears, power is transmitted via the primary shaft (A), lower layshaft (B) and final drive, while the upper layshaft (C) transmits power to the final drive in 5th and reverse only. The final drive pinions (6 & 7) on each layshaft are in constant mesh with the final drive crownwheel (5).

This design, with its three short shafts, gives the shafts a torsional rigidity which minimizes the risk of deflection at high loads and resulting poor meshing of gears.

All gears are synchromesh, including reverse. This means even reverse can be engaged without crashing the gears, even if the transmission gears are not completely stationary at the time.
The configuration of the gear trains and synchromesh units on the shafts is as follows:

Primary shaft (A): consists of the input shaft (2) and 1st (8), 2nd (9)and 5th (10) gears, 4th gearwheel (11), 3rd/4th synchromesh unit (12) and 3rd gearwheel (13).

Lower layshaft (B): final drive pinion (7), combination 1st gearwheel and intermediate reverse gearwheel (14), 1st/2nd synchromesh unit (15), 2nd gearwheel (16), 4th gear (17) and 3rd gear (18).

Upper layshaft (C): final drive pinion (6), reverse idler gear (19), reverse/5th synchromesh unit (20) and 5th gear (21).

Each synchromesh unit consists of a hub (22), the synchromesh sleeve (23), two balk rings (24) and a sleeve dog clutch (25).

The final-drive crownwheel(5) sits on the differential casing, which contains the differential and driveshaft drives.

The teeth on most of the gearwheels are machined after hardening to make them as silent running as possible. They mesh well, thanks to tall, thin teeth and optimum helix and pressure angles. Even reverse has helical gears, making it as quiet as the other gears.

Putting the 3rd and 4th synchromesh units on the input shaft helps keep the gearshift forces low.