Educational interlude

Even for those of us who live in places which are essentially manual-only, city buses have conventional torque converter automatic transmissions.

We get them from ZF:


and Voith (pronounced Foyt, it’s the origin of the racing family’s name)

Americans tend to get them from Allison:


All these have something in common. No Park position. Why?

Weight. Park works by using a pawl to lock a toothed wheel thus providing a mechanical lock. If you tried this on a heavy truck or bus you’d find that if the park pawl was actually holding the vehicle the pressure exerted would be such that getting out of park could be impossible.


So there you have it. Every day we learn something new.

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