Critical bearings and directional clutch packs are lubricated by pressurized transmission oil. The gears, shafts, non-critical bearings, and other moving parts in a manual transmission are lubricated by “splash lubrication." This is where the rotation of the gears sling oil around the inside of the transmission case. In order to achieve this, a small amount of clearance between the gear teeth is engineered to allow the lubrication oil between the gears, while maximizing their efficiency to transfer power without binding.