Our latest oddity is this.

It’s a Voith L5r4z. No, I’ve no idea what, if anything, the name means but I can tell you that Voith is pronounced Foyt and is the origin of that name. I could post the accompanying description but unfortunately for most of us it’s in Danish.

So, what on earth is it? Why does it seem to have four torque converters? Wouldn’t one do? Not in this case.

To begin with the basics, a conventional automatic box uses a torque converter much as a manual box uses a clutch. It provides a means of starting and a means of multiplying the torque. To go with this you have several, or nowadays many, gears produced by witchcraft friction elements which lock different parts together or not as the need arises.

But not this one. This uses a torque converter optimised for lower speeds for lower speeds and a converter optimised for higher speeds for...you’ve guessed it. Rather than changing gear one converter is drained and the other simultaneously filled. That accounts for two converters but there are four. The other two do exactly the same job, it’s just that they drive the output shaft in the opposite direction. What that provides us is a transmission which can can change direction on the fly and also act as a brake, thus saving wear on the brakes and avoiding having to fit a separate retarder. It’s used, obviously enough, on a vehicle which changes direction a lot and has heavy braking demands.


One like this.