The torque delivered in combustion engines is not all that simple to evaluate. Also, it cannot be compared with the torque coming from a stationary engine, which drives, e.g., at constant RPMs, a large air-conditioning plant for years.

Particularly Diesel engines increase the speed of the crankshaft distinctly during the power stroke. In addition there is the sudden acceleration and with manual gearboxes, depending on the driver, the differing clutch operation. Thus, there are torque peaks, which the gearbox constructor must take into consideration.

Why then, a converter automatic can handle more easily higher torque than a manual gearbox? Because the converter almost systematically filters the torque peaks out. It is said, and not without reason, that a combustion engine with a converter automatic lasts distinctly longer than with a manual gearbox.

In addition, further predetermined shearing points are distributed through the whole automatic gearbox. What is meant here, are the multiple-disc clutches, which basically, can slip, if too much is demanded from them. The fact is, that these are actually oil-bath clutches, which also have the advantage of lower wear and tear.

If we take a look at the internal workings of the planetary gearbox, the use of multiple gearwheels becomes clear. As, e.g., the above picture shows, the force is not transferred simply from one cog to another, which is the case in manual gearboxes, but is evenly distributed from the sun-wheel to four planetary gears. These then mesh with the ring-gear. The planetary gearbox is thus, very compact and uses the gearwheels more effectively.

The efficiency of the converter automatic suffers not only because of the converter itself, but also through the complicated power flow. In addition, the pressure lubrication circulation must also be mentioned here, whereby, through it's more specific operation, it should favour the transmission of a higher torque. 12/09

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