Camshaft rotation is accomplished by the rotation of the rear crankshaft gear and an assortment of idler gears. Note that the gears are spur gears, not helical gears. Spur gears are used exclusively on the AT to minimize loading due to thrust. Gear train noise is kept below helical gear levels by the use of a high degree of surface smoothness. All gears are at least shaved; some are ground.