Another way to change 12 gears, courtesy of Eaton.

"Cé hé sin" (michael-m-mouse) 10/27/2014 at 18:50 • Filed to: None

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I've explained the modern way to engage 12 gears on your commercial vehicle.

Now, by way of something completely different, meet the Eaton Twin Splitter.

Eaton are an American components maker who realised to their dismay that the smaller UK based truck makers who used their 9 and 13 speed non synchromesh gearboxes were falling by the wayside to the gain of larger Continental manufacturers who had the distressing habit of either making their own boxes or going to ZF. What to do? They came up with the TS 12, a non synchro box whose four gears were split twice, giving three versions of each and a total of 12 speeds.

The picture shows how it worked, with a three position switch on the gear knob. Using all of the gears, not something done in real life, would see you starting in 1(1), flicking the switch to give 1(2) and then 1(3) whereupon you changed to second, put the switch back to its lowest position and so on. Using the splitter switch just involved preselecting your next position and then lifting the accelerator at which point the gear would engage all by itself. Because it was not a synchromesh box you could, with careful timing, carry out most of your gearchanging without the clutch. The downside of this seemingly splendid state of affairs was that it took a great deal of time and dedication to learn to operate the unit without a gnashing of teeth and even then if you had to lose a lot of speed in a hurry it was sometimes easier to come to a halt and start again rather than try to do several gears worth of quick downchange.

Not many operators had the time and patience to allow novices to figure the Twin Splitter out so it turned out to be difficult to impossible to sell a used truck thus equipped and the Twin Splitter faded out to remain only in the memories of older folks who love to reminisce about the good old days, "when I were a lad, we had no power steering, no heater and a twin splitter. You young ones don't know what real driving is, you don't" and so on and on. And on.

desertdog5051 > Cé hé sin 10/27/2014 at 19:20

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You did hit that right on the head. It was a wonderful gearbox for the time. Most engines only put out 290-318 hp. I learned to drive on one from an old-timer. He told me if you need to downshift on a hill, go down at least 2 gears depending on the grade.