A 4x4 actuator is an electronic device used to engage the front differential on a so-equipped, four-wheel drive vehicle. Not all types of four-wheel drive vehicles use this type of switch. The vehicles that do employ this type of actuator will also require a switch on the vehicle's dash to be turned to a four-wheel drive setting. It is not unusual for the 4x4 actuator to require several seconds to fully engage the front axle on the four-wheel drive setting.
On some types of four-wheel drive vehicles, the operator is simply required to pull a shifter-like lever, typically located on the vehicle's floor, to engage the front axle. This type of system is known as a manual, four-wheel drive system. On other types of vehicles, the operator is required to turn or push a switch on the vehicle's dash in order to activate the front axle of the vehicle and the four-wheel drive system. This is commonly known as an automatic system. The problem with this type of system is that the axle can often take from several seconds up to a minute or more to lock the axle into gear.
The delay in engagement can often result in a vehicle becoming stuck or trapped in snow, sand or any other type of obstruction that warranted the use of four-wheel drive. The 4x4 actuator in some vehicles is a thermal-type switch that requires the switch to warm up prior to engagement. Some manufacturers offer a fully electric replacement switch that does not require a warming period, thereby allowing the actuator to engage the front axle immediately when the switch on the dash is activated. For the serious off-roader, this is often a very useful conversion.
Some vehicles use a vacuum-operated, 4x4 actuator that can develop problems locking the front axle over time. The cure for this is to replace the vacuum switch or to install a manual conversion system. Many owners of the vacuum 4x4 actuator choose to convert to a fully manual system that engages the front axle instantly when called to do so. This type of conversion is very popular with hunters and off-road enthusiasts who frequently find their vehicles in four-wheel drive in order to get out of a particular area. Most manufacturers of the vacuum and electronic thermal type of 4x4 actuator recommend that the switch be engaged periodically when driving the vehicle to avoid sticking situations caused by non-use of the system over long periods of time.