Photo 1	Photo 2	Photo 3	Photo 4

Photo 1: ARB Compressor, ARB Front Locker & Toyota Factory Rear Electric Locker switches.
Photo 2: ARB RD90 front Toyota IFS Air-Locker.  Installed with Yukon 5.29 gears.
Photo 3: Exploded view of the RD90.
Photo 4: Animated gif demonstrating how the locker operates.

Here is a description from Chris Wood of ARB on how their new locker design works:

The RD90 is based on the new timed-gear design that ARB developed about two years ago. To give you an idea of what this means... when a traditional Air Locker locks up, there is no guarantee that the teeth of the side-gears and spider-gears share an equal portion of the load. In other words, the load is purely random based on how the gears are clocked to one another at the moment the Air Locker becomes locked. Strength in a traditional Air Locker is achieved by having the largest side-gears and spider-gears possible and by having four spider-gears whenever possible. This gives the individual teeth a better chance of handling the loads they will be faced with when the Air Locker is locked. C-Clip differentials suffer in this area because they usually have only two or three spider-gears and consequently fewer teeth. The timed-gear Air Locker has its side-gears and spider gears clocked (timed) from the factory to provide a perfect distribution of the load over all teeth when the Air Locker is locked. The resulting strength increase in some applications has approached 300%.

In basing the RD90 on our timed-gear design, changes were also made to the way the air is delivered. Traditional Air Lockers, as you obviously know, receive their air at the bearing opposite the ring-gear. The timed-gear Air Lockers receive their air at the bearing on the ring-gear side. This means that on the IFS Toyota the air line enters on the small side of the split case. In addition to this change, the timed-gear Air Locker also benefits from a two-piece case instead of the traditional three-piece design and we have eliminated the need for the annular piston used to transmit the air's force to the locking clutch-ring. In a nutshell, the RD90 is stronger, simpler in design and easier to install than a traditional Air Locker... especially in IFS applications. Regarding the installation instructions, they have been revised to coincide with the unique set-up procedures of the RD90. Sorry for the long dissertation here, but you seem like a person who would appreciate some of the details. Hopefully this helps.

E-Mail to Erik Bibelheimer from Daniel J Bongard (MEng) AIR LOCKER DESIGN:

Currently the application list reads along the lines of ALL TOYOTA IFS EXCEPT LANDCRUISER.  I can't find anything to prove that wrong yet.  You were a big help in establishing that, and if I hadn't been able to come up with that info telling us how common that diff is then we probably wouldn't have pushed it to the front of the line like that.  It'll even beat the Isuzu IFS (RD94) to the shelves and that one was started  many months earlier.  I personally installed the prototype into ARB's 2000 Tacoma, so that one definitely fits, although its not an easy task to swap centers in that style of housing. Toyota should never have welded the cross member in and definitely should have left it an adjuster nut set-up.

On the tech side of things you might be interested in the fact that we ditched the needle bearings on the stub shafts in favour of a teflon  impregnated sintered bushing that was designed to meet the abuse-quota even when dry (oiless).  That allowed us to thicken up the journal cross section which Toyota had left too thin as a result of adding that needle bearing as an afterthought.  It also gets rid of that sloppiness that can be felt in the Toyota needle bearing. Might even prolong CV life as a result. Time will tell.  Beyond that, the RD90 features the newest locking mechanism style currently only available on the newest Chrysler 8.25 and Ford 8.8 'INDESTRUCTIBLE' models.  I also tried very-very hard to correct the 'broken Toyota retaining clip' problem on the stub shafts.  The geometry on the inside of the gears will retain the clip equally as well but should compress the clip gradually when extracting the stub shafts.  You'll still probably break a clip when you pull them out of you factory diff when making the change, but hopefully that should be the last clips you break! ARB is not interested in Toyota's desire to sell you replacement clips.

BTW, running a detroit in an ADD IFS without intalling hubs on that model risks a lockup at driving speed which will instantaneously bring your drive shaft up to speed by driving it with your ring gear.  A darn good way to blow up a ring and pinion set!  Personally, if it were my rig I'd at least put one hub on the non-ADD side of the axle either way.  It'll save wear and gas.  And hubs on bothsides would mean your CV's would be brand new when you needed them most.

ARB RD90 Breather Install, Text & Photos By: Lars Dennert

If you have an ARB locker up front and you are experiencing heightened breather issues such as oil coming out the breather, here is another possible solution. Due to the fact that the stock breather is very small, very low on the diff housing near the oil and has many bends in the line, it takes only a small amount of internal pressure blow oil out of the breather. One solution is to lower the fluid level about 1/2". If that doesn't work you can try adding a second breather. Here's a tip from Daniel Bongard at ARB.

Take a rear axle fill plug and drill through it with a 3/8" bit. Then tap the hole with 1/4" NPT (which is about 3/8").

Screw in a 3/8" barbed NPT fitting and then install it in the diff. Ideally some of the housing should be ground away on the left side to provide more room to tighten down the fittings. However the fill plug does not have to be very tight.

I installed some cheapy clear 3/8" hose so I could monitor how far the oil travels up the tube. On the engine compartment end I installed a cheap fuel filter.

Additional text by: Steve Schaefer, I used the actual Toyota breather end part number: 90930-03136 and a rubber black hose.  It took me 3 to 4 tires to get a really nice straight tap in the drain plug.  I ended up drilling the hole out a hair more than the tap recommended and finally got a nice straight tap.  This setup works great and I have not had any more gear oil pukeing from the front diff.

Excellent write up on a RD90 install in a Tacoma.