The space between two gears. Usually used to describe the space between the spur gear and the pinion or clutch. If the gears are too tightly meshed (too close together), they will slow your car or truck down. If the gears are too loosely meshed (too far apart) they will strip easily. To achieve a proper mesh, put a piece paper between the two gears and move the gears together. Secure the gears in that position and remove the paper. After time, you'll learn how to do this without a piece of paper.