What is the difference between old and new technic gears?

[Legofan4ever88]

I'm planning on building a lego coin pusher(non-mindstorms at first then will be setting it up as mindstorm run[i hope]) and when I went to look at gears on bricklink, i noticed there was some listed as "Old" and some as "New". What's the difference? Which is more sturdy?

[Silcantar]

New gears are generally stronger, because certain designs in the past have been prone to breakage under high torque. Lego has redesigned several gears in the past to increase their strength. If your MOC does not require large amounts of torque, it probably doesn't matter, although you may want to get the stronger gears in case you do eventually build a MOC that stresses the gears more. One gear to avoid in any circumstance is the 14-tooth bevel gear, though, as it is prone to breakage under relatively small stress.

[DLuders]

TechnicBRICKS had this article about the redesigned 16-tooth Lego Technic Gear. Here are the old and new versions:

Jetro and Sariel pointed out the three different types of Lego Clutch Gears. Scroll 1/2 the way down Sariel's Gears Tutorial to read about these:

Scroll 3/4 of the way down that same Gears Tutorial to read about the three different types of 8-Tooth Technic Gears: