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The straight cut gear (reverse) is on the left. The helical cut gear (1st) is on the right.


Helical cut


straight cut


Straight cut gears, like reverse, are very noisy, but they have stronger teeth with more surface contact and will last longer for racing.

Helical cut gears have very little of the teeth's surfaces in contact, and are very quiet, but are also weaker than a straight cut gear.

Helica cut gears are more difficult and expensive to manufacture (they are actually an "involute" profile, which is much more difficult to machine).

The involute is a mathamatically derived profile that maintains a constant gear speed as the portion of the gears in contact is constantly changing diameter. That is so that you don't have the gears speeding up and slowing down to maintain a constant vehicle speed, which would eventually tear the gears apart from added stress.

Here, read this.

Edited by Vulcan Grey


Vulcan Grey 89SE


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i looked around google and nothing shows up. What is the difference between a dog cut gearbox and a heli cut gearbox?



I'll give you my interpretation--- whether you like it or not...

A "dog cut" gearbox is refering to the method of selecting gears. Specifically the "shift dogs". This is a device that does roughly the same job as the synchros, except that it just locks the gear to the shaft without taking the time to equalize the speed. This is identical to how a motorcycle gearbox works. They shift very fast, and that's the ONLY way they shift--fast. In automotive use, a dog cut box is used only in race gearboxes that typically only have straight cut gears. As you could imagine, this gearbox would be a pain in the ass on the street.

A "helical cut" gearbox would typically have conventional sychros, and thus would be more appropriate for a "street" type of gearbox.

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