ARB RD01 conversion to RD23 and add 529 Nitro Gears
(97 low res pics loading)
MAR 2 2009

Matt, from Bakersfield CA, shipped me two 4-cyl 3rds that have the old style RD01 ARBs(45mm journals) in them already. The plan is to break-down the ARBs and convert them both to RD23(50mm journals) for installation in a rear V6 carrier and a brand new HP carrier from Allpro. This link is only for the hi-pinion install. 529 Nitro Gears from are also going in.

Old style 4 cylinder RD01.

serial numbers on the case.

The arb is removed from the 4 cyl carrier.


As received from Allpro.



Everything is here to do the change-over.

This is all the stuff sent from ARB to convert it for use in a V6 carrier.

Here's the master install kit. The 4 bearings have been cryo treated for superior life.

The RD01 has the smaller 45mm journals in order to fit the 4 cylinder carrier bearings. The ends (lid and flange) will be replaced to allow 50mm V6 bearings to fit. Shown is the 529 reverse cut Hi-pinion Nitro Gears that have been both HEAT and CRYO treated.

The old oem pinion flange will be replaced with a new multi-drilled flange.


The old one had a fair groove in it and I was concerned about a potential leak.

The new one :)

The old flange cap is removed.

The splined sidegear is next.

Now to flip it over and remove the arb lock tabs. Red loctite will be used instead of these tabs upon re-assembly.

An 8mm 12 point socket easily takes off the 6 bolts that hold the cylinder cap on.

The orange piston seal can be seen on the left...the sidegear and plastic piston are on the right.

The 3 soft metal retaining pins come out easy.

The 3 cross-shafts can now be removed.

The spider block now comes out...

...and so do the 4 spiders with the worn thrust washers.

Last, but not least, the sidegear and thrust washer.

That pretty much does it but I was curious what the return springs looked like that keep the plastic piston in the unlocked position with so much determination.

To me, it feels like it takes 80 pounds of physical force to push the piston down(about 1/2") into the locked position.

A simple twist, a light pull, and it comes off.

These are the 4 springs that return the arb to the unlocked position when the air is released.

This clutch gear is what actually couples and locks it together.

This main center section is now fully stripped down and now to put it all back together with new thrust washers and end caps.

New thrust washers for the pinions (spiders)... thrust washers for the sidegears.

This looks like the US GEAR logo on this sidegear.

Grease helps hold the thrust washers in place.

With some fumbling, the pinions can be aligned and the 3 cross-shafts will slip through...

...and success was eventually accomplished.

The 3 retainer pins just drop in place with gravity.

Some new oil for the thrust washer.

This is the old cylinder cap with the soft orange piston seal.

The new design involves an upgraded cap with a 'bonded' piston seal.

Now the cylinder cap covers it.

Red loctite is applied to the threads.


New gear oil and a new thrust washer on this splined sidegear. Look closely and notice that I did not notice the old washer was still on the sidegear.

One more check...the spiders all turn very smoothly.

Sidegear is layed in place...

The flange cap is lined up...

hmmm....a slight gap. Then I discovered that I had 2 thrust washers on that sidegear. Problem corrected and then the lid went on all the way and the sidegear would actually turn when I reached my finger inside the journal. All was good now.

The ring gear required a little coaxing.

The flange cap was fitted in place and red loctite was applied liberally to the 10 ring gear bolts.

Cross-tightened with 75 ft/lbs.

These are the parts I replaced to convert the rd01 to an RD23(45mm to 50mm).

The carrier bearings were a very tight fit but the press made easy work of it.

The new races(cryo treated) were also pressed on.


The protective coating on the pinion was burned off during the heat treatment process but it left some residue.


I will press on the new cryo bearing with a .080" shim for the first try.


I can install the pinion now without any sort of crush or solid collar and tighten the pinion nut until about 10~15 in/lb is reached for PPL.

The ARB case is installed and the bearing caps are tightened down in preparation for a pattern check. Minimal carrier bearing preload is set and backlash is set in the ballpark of .008" for this preliminary check.

A nice, wide load bearing but it's too deep...need to remove some pinion shim.


The pinion tooth looks to be favoring the outer edges. Shallow on the pinion means deep on the ring tooth.

The load bearing is favoring the edges...that means shallow here and implies deep on the ring tooth.

I pulled it apart and removed .0035" worth of pinion shim. This is overall good. The patterns are varying from tooth to tooth which I have no control on.

The coast is good.

Because of the low shoulder design of the solid collar, I had to clearance the inside of the oil retainer.

I made use of an oem Toyota solid collar because of the bell shape.

Now the solid collar will not rub on the retainer.

It took 4 tries to get the right shim thickness for the collar.

Now the shop flange can be removed and the new seal installed.

A light coating of gear oil on the flange underside will minimize the added drag of the seal's dust cover.

RTV was added to the flange splines to prevent any possible oil from sneaking up the splines. Loctite on the pinion nut is added insurance.

By tightening the nut extra tight, I was able to get the PPL preload close to the upper limits.

Ding the nut and this end is done.

The ARB case is installed and the bearing caps are temporarily bolted in place. The oil seal assembly was lubed up and carefully wiggled in place.

The soft copper line is gently routed in the neatest possible fashion.


It's alot easier to route the copper without the brass bulkhead hindering things.

The copper line is nicely centered.

With the copper line routed and cut to length, now the ARB case can be permanently installed. Anti-seize is generously splashed on all the threads.

The 4 cap bearing bolts are tightened to 75 ft/lb and the wheel adjusters are tightened to 150 ft/lbs while guiding the backlash to .007 or .008". Remember from my earlier links that 150 ft/lbs on the wheels translates into 15 in/lbs of actual CBPL carrier bearing preload.

120 in/lbs on the lock tabs....with loctite.

One more pattern check...looks even better than before.

coast is good.

This is my compressor that I use to air up my tires after the trail rides. It also sees ARB leakdown test duty.


Did not budge a smidge even after 30 minutes.

Through the case, I can see the locker teeth engage....

...and dis-engage when the air was released.

Just a final BL check on every other tooth for about 21 measurements.

Some documentation...

...some more documentation in the form of the notes I took during the rebuild process.