Track/Kick Rear Air Locker
Project Sidewinder/ARB part 2
with Bill Johnston
As Track/Kick owners have noticed, the number of aftermarket traction aids available for the larger rear third member is rising. With the growing number of hybrid rear axles available for the Samurai, this makes the Sammy owners ears perk up as well. We prepared this Tracker differential, stuffed with factory 5.12 gears, for the Sidewinder/ARB project we started last month.
ARB has an air locker to fit both ring and pinion combinations that are found in the rear diffs from 1988 and up. From 1988 to 1993 Suzuki used a 10 bolt ring, this uses ARBs RD74 model. In 1993, Suzuki started putting a 12 bolt model into the rear differential. This is what we were working with, so ARB supplied the RD79 model for this installation. Both flavors of ring gear were used in 1993, so if you have any question as to what you have, there is a quick way to find out without pulling the whole thing apart.
On the drivers side of the differential, there is a speed sensor that is held in with a 12mm bolt. Remove the sensor and look inside with a flashlight. Mark the first bolt head you see with a marking pen and then rotate the pinion. Count the bolts as they go by... Of course this is easier when the axle is out and in the shop, common sense says that you don't try this on the vehicle with the tires on the ground.
Let me start by saying that if you are not comfortable with working on your own gearing, this is probably not the place to start unless you have someone with a little experience showing you how. If you don't set the backlash correctly, or you end up with spare parts... it will get expensive fast.
|That said, we started with the third member bolted to the workbench. Before disassembly, we marked the bearing caps with a punch and then marked the third member casing to match. One dot for the left side and two dots for the right.
|Next we removed the caps and set them aside. Notice the cool tool I used to hold everything steady... I found that a birfield stub has 26 splines, just like the rear axle. I keep two grenaded birfield stubs with my 'specialty' tools for working with rear differentials. They are easy to hold onto and they allow you to easily turn the splines on the bench. Next we just lift the carrier out of the casing and move the casing to the floor.
|The bearings on this carrier were in excellent shape, so we decided to reuse them. We removed them easily using a bearing puller. Make sure you get the ends of the arms all the way under the center portion of the bearing or you could just rip the outer cage off - thus destroying the bearing.
|Flip the carrier over and repeat the procedure on the other bearing. Here you can see the 12 bolts holding the ring on the carrier. You can also see the teeth that the speed sensor (mentioned above) counts in the photo to the right. After reassembly, you will no longer have those teeth to worry about.
|Next we remove the ring gear bolts and carefully remove the ring gear, setting it aside.
|Now we turn our attention to the ARB Air Locker. You will notice when you press the bearings back on that one of the bearing journals is longer than the other. This is the way they get the air into the center of the carrier... The journal is plumbed to move air from a seal housing on the longer section - into the heart of the carrier. This is the side that should be facing up when you put the ring gear back on.
|Looking closer at the new carrier, you will notice that the flange thickness is as thick as the old carrier (with the speed sensor gear). Since you will be using the new carrier, the sensor gear will not be a part of the assembly. Tighten the bolts in a cross pattern and finish up with a torque wrench.
Factory Service Manual recommends that the ring gear (aka - drive bevel
gear) bolts get torqued to 58-66 ft-lbs.
Next you have to find the best location for the air line to enter the case. The key is to keep it away from the gears, but still make sure it clears the axle housing when the third member reinstalled.
|After marking the best location with a punch, we drilled a pilot hole and then followed it up with the 7/16" drill bit for a final hole.
|You can see the final location once we cleaned up the hole. This is going to accommodate a 1/4" NPT fitting, so the next step is to tap it with the correct type of tap. This is a thin section of the case, so you don't want to have to do this twice and run the risk of making the hole too large.
|Teflon tape should be a staple in a toolbox. Seal the threads well and install the fitting in the new tapped location. This seal isn't for air, the system never pressurizes the axle housing. This is more to keep all the lubricant in the housing if you get a little radical on the trails.
one likes an oil leak, especially when you were the one that did the
Don't torque it down too much, remember that you want it to seal without stripping out the new threads.
|Now that the bulkhead body (correct name) is installed in the housing, it is time to work on the tube that gets the air from the fitting to the locker. Start with selecting the correct compression nut and ferrule. There are two ferrules that come with the installation kit, but only one of them will fit correctly on the tube. See the photo to the right.
|Putting the carrier back into place, use your hands or an appropriately sized tubing bender to form the tube up and over the bearing cap and around the carrier body. The seal housing (the ring on the end of the tubing) will end up oriented with the tube coming up just to the right of the locking tab on top of the bearing cap.
|While forming the correct bends in the tubing, you can allow the seal housing to rotate counter-clockwise a little to make room to make the final bend where it will go into the bulkhead body that we just installed. Now we fit the tube for trimming.
|ARB has provided a tube that is more than long enough to take care of this application. So we have to trim it after putting everything back into place. A permanent marker will allow you to mark where you will have to cut it. We suggest using a tubing cutter to make this cut, as most anything else will deform the tube which could lead to air leaks later on.
|We fit the tube and seal housing in its approximate finished location and then gently bent it out of the way so we could fir the carrier into place. When you look around inside the empty case, you can find a couple of other places you could mount the air tube bulkhead body. I took a look at least two where we wouldn't have to drill the case.
|But neither of the locations allowed enough clearance between the ring and the case for the line to go between with a margin of safety. So when all else fails... follow the directions from the carrier manufacturer (which, by the way, was very well laid out and detailed. Thanks ARB). With the air line out of the way, the carrier goes back into place (to stay this time).
|The easy part is the ring side of the differential. We just reassembled it exactly the reverse of its disassembly. Don't lock down the bearing cap bolts until you are done with backlash adjustments later. The other side gets a bit trickier because it has to house an airtight seal for the locker. It starts with a small clamping plate that has been tapped for three allen screws.
|Next came the adjustment ring. Notice that it looks a little different than the stock unit. Be careful when working around the extended bearing journal because it has to be perfectly smooth and scratch free to keep the seal air tight. Next we installed the bearing cap bolts, but, like the other side we kept it loose enough to make the backlash adjustments needed.
Backlash is measured with a dial indicator. The pinion must be immobilized (held perfectly still) and then the dial indicator is used to measure the amount of movement the ring gear still has. The Factory Service Manual says the measurement should be between 0.004 and 0.006 inches. The adjustment is controlled by running in one adjuster ring and running out the opposite adjuster equally. Turning the adjuster one notch changes the backlash by about 0.002 inches.
|The o-rings are the most critical part of the air seal. When installed, they create an air chamber that 'floats' on the bearing journal. The air comes in through the seal housing and is plumbed through the journal wall into the interior of the carrier. Give the o-rings a good coating of oil before installing them in the seal housing.
|Also make sure the o-rings aren't twisted in the grooves. Click on the photo to the right (you can do this with any of the photos) to get a good look at how the two o-rings border an air channel that we talked about earlier.
the seal housing onto the bearing journal, you should use a gentle
twisting motion. Don't pinch the o-rings as they slide over the end. Pay
special attention to the notch just left of the air tube. This is where
the bearing adjuster stopper has to line up with an open notch on the
adjuster ring. See the center picture below to see it in place. Using
a small screwdriver we aligned the bolt holes in the seal with the tapped
holes in the clamping plate we installed at the top of this page. We added
the three cap screws using locktite to make sure things don't come loose
later on, but at this point we left them finger tight.
Now here is a step often neglected but very important. This is where you bench test the system and center the seal housing all at the same time. Applying air (90 psi) to the system, and then rotating the carrier will center the seal housing. At this point we slowly tightened the cap screws to 3.5 ft.lbs. If you over tighten the cap screws you will deform the clamping plate and that could cause premature failure of the seal when the cap screws fall out.
This is what it should look like when it is finished. Notice how the air tube has sweeping bends and stays away from the gear teeth. The locking tab has been put in place and the unit is ready to go into the sidewinder axle we installed in the last issue.
|On the left you can see the 26 spline axle in a normal ARB side gear from this months installation. On the right you can see how much larger the opening is in the 27 spline side gear when we put the same shaft into it. These side gears are a direct replacement and can be ordered separately from your ARB distributor or already installed in a new ARB air locker prepared by the shop you get your 27 spline shafts from.
|Next issue we will show you how to convert an existing (Samurai) ARB 26 spline rear carrier to fit the 22 spline front axle in a Samurai. That way you can just move the ARB you spent money on last season to the front and end up with two air lockers.
Check out part three of this series and see how easy it is