If you've kept tabs on our '04 4Runner build, you know we've been using an automatic locker in our Currie 9-inch rearend. The automatic locker has done everything we've asked: It's been self-contained, automatic, and maintenance-free. Why change? It wasn't the noise factor, as the occasional clunk or pop wasn't a big deal. It wasn't the handling, as it was easy to adapt our driving style. The locker unlocked when coasting and locked up when accelerating. What was the reason? The deciding factor was tire wear.
Since there's no way to turn off an automatic locker, we ended up scrubbing the tires every time we accelerated out of a turn. Had our 4Runner been a weekend-only trail rig, the tire wear would've been a non-issue. This isn't the case, though. This particular 4Runner drives to and from the trailhead, as well as to the grocery store and the office. Yeah, it gets groceries. So what?
A dual-duty vehicle like our 4Runner is a perfect platform for the ARB Air Locker. Unlocked, the ARB acts as a street-friendly, tire-friendly open differential. When locked, the Air Locker becomes a spool, turning both wheels in complete unison. The ability to choose between wide open or full on makes the Air Locker a no-compromise traction solution.
Yes, there's a downside. The very thing we loved about the automatic locker is the very reason we initially shied away from the Air Locker. Air Lockers aren't self-contained. They're actuated by air (duh) and hence need an air source. Not to worry, as ARB offers a wide range of compressors. Installed correctly, the complete Air Locker system should be stone reliable.
Air Lockers are going in both ends of this 'Runner. We'll cover the rear diff this time and complete the process later on with the front. ARB's Air Locker: a diff for all occasions.