Automobile transmissions - Influence on vehicle performances

We saw in a previous article [BM 2 582] why a gearbox was essential and how it could complement the engine to ensure the vehicle's propulsion by adapting to the conditions of use.

This article goes even further to show that the gearbox plays a direct part in vehicle performance, whether in terms of top speed, acceleration or crossing ability...

But we can't deal with these aspects without introducing some basic notions of longitudinal vehicle dynamics.

Indeed, vehicle performance in terms of clearance or acceleration potential, to name just two examples, is a function of the overall torque that the front (or rear) axle is capable of "transmitting" as a function of the weight applied to it and the grip at the wheel-road interface.

In the final analysis, the vehicle's acceleration or crossing capacity incorporates the performance of the GMP (engine and gearbox), which may be higher or lower than the wheel is able to accept.

As we can see, in addition to the now well-known notion of engine/gearbox pairing, that of GMP/vehicle pairing takes on a special meaning.

Here, we show why, and try to do so in the most accessible way possible. From the latter point of view, examples are often instructive. So we've chosen a few to illustrate our point.