All gears are categorized by type and number of teeth. Teeth vary from type to type.
The technic gears system is the most well known and is compatible with almost every type of LEGO even Duplo and Primo in some fixed cases. The following list tells about all the Technic gears, ordered by class then teeth.
A system of gears which can generally connect only on 90degree angles, althogy a few are capable of connecting vertically or horizontally.
- 12 tooth bevel gear — a small gear which can only connect at 90 degree angles. Its back is flat with a small ring poking out, and two placed back to back can create an interesting pulley.
- 14 tooth bevel gear — a gear slightly larger than the 12 tooth bevel gear. This gear is capable of connecting at angles and 2 dimensional areas. This gear cannot connect to other bevel gears.
- 20 tooth bevel gear — a gear slightly larger than the 14 tooth which has the same principle as the 12 tooth, including the ring on the back.
- 12 tooth double bevel gear — twice the thickness of its thinner bevel counterpart, the 12 tooth double bevel gear can connect on sides of 2-dimensions and 3 dimensions.
- 20 tooth double bevel gear — same as the 12 tooth double bevel gear other than the fact it has 20 teeth. This gear's teeth are thinner than other gears.
- 36 tooth double bevel gear — same as all double bevel gears capable of fitting three axles and two pegs in the middle.
A system of gears which is compatible with other gear systems through specific connections.
- 8 tooth gear — the smallest gear in the system. A little smaller than the 12 tooth bevel gear. The 8 tooth gear resembles a nut with eight pointy daggers coming out.
- 16 tooth gear.
- 24 tooth gear — a gear which can hold 4 pegs and in some varieties 4 pegs and 3 axles. It is almost the size of a 20 tooth double bevel gear.
- There exists a 24-tooth slip gear as well; it is identical to the 24-tooth gear, except that it protects against input stall should the output become locked in some way.
- 40 tooth gear — the second largest in the lego system this gear is the largest primary gear. Capable of fitting 16 pegs and 4 axles this gear can have a lot of mountings.
A series of gears that are rare and hard to find. They consist of gears with a tooth count of a multiple of three or seven. Very few go out of that range. Their teeth are like fat bevel teeth.
- 9 tooth gear
- 14 tooth gear — another odd gear, it connects to the 14 tooth and 9 tooth by a means of half stud connection.
- 15 tooth gear — a classic secondary gear which comes in two variations as stated in the text above.
- 21 tooth gear — the 24 tooth gear of the secondary gears it is useful and can connect on right angle with the 15 tooth gear.
- 35 tooth gear — a huge gear that comes in two varieties.
- 42 tooth gear — the largest gear.
- Tricker — a gear which has four huge boulbous teeth. It can connect in any direction even on angles under 180 degrees.
- Hailfire droid wheel — a gear with 176 teeth, but no central axle mount.
- Worm gear — a gear with one tooth spiraling down. Worm gears can turn gears and pulleys but others cannot turn it, making it an ideal lock device.
- Differential 1 — a long gear with 28 teeth on the back and 13 on the front used for connecting bevel gears to primary gears by fitting three 12 tooth bevel gears inside. It uses peg connections for the movement of gears inside.
- Differential 2 — a long gear with 28 teeth on the back and a plain peg hole on the outside it houses three 14 tooth bevel gears inside for its connection.