One of the best features of the fifth-generation 4Runner is the availability of a selectable rear locker straight from the factory. This option is one that can really help the 4Runner get into deep terrain, but our 4Runner isn't just going in to deep terrain on exploratory trips-it has to get out, too. To ensure we have maximum traction when we need it, we decided to add a selectable locker to the frontend.
With a track record for ruggedness and reliability, we decided on the Air Locker from ARB. The Air Locker uses a fully machined differential case made from nodular iron, while many other components are made from the highest-quality aerospace-grade alloy steel. ARB designs the Air Locker to be stronger than other stock drivetrain parts and carries out destructive testing to ensure the end user gets the best possible product.
ARB's Air Locker works by replacing the stock open differential unit with the pneumatically operated ARB locking unit. A 12-volt compressor with a small air reservoir is wired and mounted to the vehicle and operated by a remote switch, usually mounted on the dash. A second switch, also mounted on the dash, opens a solenoid that releases pressurized air from the compressor reservoir, engaging the locking mechanism. Unlocking is as easy as depressing the switch, where the only noise you'll hear is the pressurized air venting to the atmosphere with a familiar "pssssh."
Able to lock and unlock the front end at the press of a button and while moving in a straight line up to 60 mph, the Air Locker is there when you need it, but invisible when you don't. When the locker is unlocked, it acts as an open differential, which means that around town and on the highway, there is no difference in how the 4Runner drives from stock, with no negative characteristics such as binding, popping or torque steer common to automatic locking differentials. This makes the Air Locker an excellent choice for the front of any vehicle, especially those that see use on pavement and off.
For the install, we headed down to Off Road Evolution in Fullerton, California, where we documented the installation of the Air Locker on Project 4Runner Backcountry.