The simplest 3-speed hubs use a single planetary epicyclic gearset. The clutch pack activates a planetary gearset which causes one wheel to be overdriven. In 4WD Low, the input torque is multiplied through a 2.72&colon;1 planetary gearset. A Simpson gearset delivers three forward gears and one reverse, plus neutral. Many cordless drills incorporate this type of torque limiter in a planetary gearset. In addition to the clutches, this transmission has a second planetary gearset. Low and Reverse ranges were a 1.82 ratio reduction, using a single planetary gearset. The latter was the first to utilize the Simpson compound planetary gearset. In such a gearset, gears having smaller radii and less inherent mechanical advantage are used. Honda could not make a conventional planetary gearset automatic transmission without infringing on any patents. The torque limiter is typically the last gearset in the transmission. The new transmission was built around the Ravigneaux planetary gearset of the "X" transmissions. It was mated to the Quad 4 engine and uses a 3.77/2.19/1.38/1.03/.80/3.94 gearset. Note that there is no differential gearset in this design. Nevertheless, some new cars are still sold with automatic transmissions based on the Simpson gearset.