well. Nissan Corporation's electric locker can be found as optional equipment on the Frontier (Navara) and Xterra. Ford offers an electronic rear locker on the F-series and Ranger trucks. Toyota currently offers a rear e-locker on the Tacoma and 4Runner (TRD Off-Road and TRD Pro trims only), but has also offered front and rear e-lockers on vehicles such as the Land Cruiser in the past. Pros: Allows the differential to perform as an "open" differential for improved driveability and maneuverability, and provides full locking capability when it is desirable or needed. Cons: Mechanically complex with more parts to fail. Some lockers require the vehicle to stop for engagement. Needs human interaction and forward-thinking regarding upcoming terrain. Unskilled drivers often put massive stress on driveline components when leaving the differential in locked operation on terrain not requiring a locker. Spool A spool is a device that connects the two axles directly to the ring gear. There is no differentiation side to side, so a vehicle equipped with a spool will bark tires in turns and may become unmanageable in wet or snowy weather. Spools are usually reserved for competition vehicles not driven on the street. Mini-spool uses the stock carrier and replaces only the internal components of the differential, similar in installation to the lunchbox locker. A full spool replaces the entire carrier assembly with a single machined piece. A full spool is perhaps the strongest means of locking an axle, but has no ability to differentiate wheel speeds whatsoever, putting high stress on all affected driveline components. The internal spider gears of an open differential can also be welded together to make a locked axle; this method is not recommended as the welding process seriously compromises the metallurgical composition of the welded components, and can lead to failure of the unit under stress. Disadvantages Because they do not operate as smoothly as standard differentials, automatic locking differentials are often responsible for increased tire wear. Some older automatic locking differentials are known for making a clicking or banging noise when locking and unlocking as the vehicle negotiates turns. This is annoying to many drivers. Automatic locking differentials also affect the ability of a vehicle to steer, particularly if a locker is located in the front axle. Aside from tire scuffing while turning any degree on high friction (low slip) surfaces, locked axles cause understeer and, if used on the front axle,