Here's How Dog Box and Sequential Transmissions Work

Illustration for article titled Here's How Dog Box and Sequential Transmissions Work
Screenshot: Donut Media

Race cars can get all sorts of crazy goodies that street cars don’t get, especially when it comes to gearboxes, because wasting precious seconds shifting from gear to gear in a basic-ass transmission just won’t do in a race. Enter: dog boxes.

So named for the dog “ears” that protrude from the gears, dog box transmissions are straight cut (as in the photo above), not helical (spiral cut) as in street transmissions. This allows the driver to jam the car from gear to gear, and they are bigger and beefier. Look at how big and beefy those dog ears are.

The downside is greater wear and tear on the gears themselves, which race teams don’t really care about, since that’s just the cost of doing business.


But let’s be honest, there are no downsides to a dog box, and they’re not just for race cars. Take the one on the Fiat 500 695 Biposto, for example. The fun of a dog box is that the optimal way to use it is basically the opposite of what you’ve been taught your entire life about shifting gears in street transmissions. Forget about slowly releasing the clutch and easing on the throttle to put the car into gear. A dog box transmission is all about violence, with rapid fire gear changes at high revs without a clutch, the quicker the better. The gear’s teeth are cut longer to accommodate such shifts. Street cars have synchronizer rings, which are soft and help guide the car from gear to gear, which is comfortable. As for un-synchronized dog boxes, there’s nothing comfortable about it from a passengers’ perspective. From a visceral standpoint, though, it’s hard to top. (Formula Drift car builders, as usual, have the right idea.)

Donut Media explains all of this and more in their latest video, which also gets into sequential transmissions.

You can jam through your helical street transmission if you want, but it’s generally a bad idea, unless you want to replace your gearbox like a real race car driver every 10 minutes or so. Street transmissions are designed to be quiet and smooth, not for performance. Which is fine! Driving slow is underrated.

News Editor at Jalopnik. 2008 Honda Fit Sport.

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You can, in fact, get helical gut dog gears. The gear-gear interface has nothing to do with how the gears are connected to the driveline. if you could have a theoretical flat surface with a friction factor of 1, that would work as well.

Straight cut gears provide less friction, better durability, and higher torque capacity due to the larger gear teeth and solid interface between teeth than an equivalent helical gear

edit, forgot to add gif