This of course, is not an exact portrayal of a formula-one gearbox. This would probably have straight cut gear-teeth because it's designed for efficiency and not for quiet running. Moreover, the gear changing here is done electrically or electro-hydraulically. This way the number of the gears can be even higher. The synchronisation in a gearbox like this is also not essential. However, the basic construction of the gearbox remains the same.
With straight mounted engines, a combination of bevel- and crown wheels is always necessary, however, normally placed behind the gearbox in the final drive. In the case of the Porsche Carrera GT it is mounted directly behind the clutch at the entrance to the gearbox (arrow pointing down). Because of the multi-disk clutch, the engine can be mounted quite low which accounts for a low centre of gravity.
At first sight the illustration above seems a little bewildering. The light grey gearwheels are mounted higher and therefore above the two actual gearbox shafts. The letter 'S' indicates a possible locking differential. Here, the right axle drive shaft can be directly flange-mounted. (right arrow) The other arrow points to the possible position of the left axle drive shaft. Because of the wheel diameters, both shafts are placed notably higher than the crankshaft.
What does the power flow look like? The front gearbox shaft is driven by the center of the crown wheel. All the wheels are solidly linked with the shaft, reverse-, 1st and 2nd gear are found on the right hand side, 3rd to 6th gear on the left hand side. All the wheels mesh with the running wheels of the rear (lower) gearbox shaft, except the crown wheel and the reverse gear wheel on the extreme right, which is connected by a small idler-gear with the respective running wheel.
During gear-changing, you will now notice hardly any difference to other gearboxes. The rest of the power flow is quickly explained. Instead of one larger gear ratio to the final drive, there are, probably because of the compact construction method, two smaller ratios, through two gearwheels on another intermediate shaft above the rear gearbox shaft. Between them, opposite to the bevel wheel, the drive-spur-gear is connected to the horizontal shaft mounted above. The power is transferred to the rear axle by the (grey) wheels in the above drawing.
This shifting system was specially designed for the Carrera GT. Supposedly, the connections shown in green and blue to the lowest (shifting) shaft are made up of ball-bearinged steel bands. On the selector rod beforehand, the shift-forks, differently to all others, can be individually moved. Depending on which way the selector shaft is rotated, one of the differently arranged claws will always only grab one shift-fork. This then moves either to the right or to the left depending on whether the gear-lever is moved up- or downwards. 12/07