A D44 with an Ox Locker
Installation in a '89 Jeep Cherokee

by Andreas Ritterbusch
Posted: September 18, 2001
Last Revision: August 26, 2007

Here are some images of my rear D44 project with an OX locker. The Ox locker is a relatively new locking differential, with a manually operated cable mechanism. This sort of locking device was long overdue, in my opinion. ARB has been the only manual locking device on the market until now (besides OEM versions found in some Toyotas and most of the Mercedes G-Class). Some excitement also exists about Tractech's as of yet not available Detroit Electrac. Something along the lines of the Electrac is also the electronic ECTED locker by Auburn Gear. It appears, though, that Auburn Gear is targeting the automotive industry, rather than the individual with this device.

I opted for the Ox locker since I believe that ARBs can be tricky, not only to install, but also to maintain. Left without a choice, I eventually would have gone the ARB route, but was very glad when the Ox locker became available with its entirely manually operated mechanism.

The Ox locker is available at Drivetrain Direct, etc. The Ox is available for the D30, D35, D44, and the D60, among others. There are also so-called "Super kits" available for the D35 and D44. These kits come with bigger axle shafts (higher spline count) from Superior Axle. These kits are roughly double the cost, and make everything highly "custom". I was tempted to get the SuperD44 kit, but price was too high (would buy another Ox for the front). I preferred to keep the axle shafts, bearings, seals, etc. at OEM specs for now. I got a cheap used second set of rear axle shafts for my D44 instead. Perhaps in the future, I might get some alloy axle shafts from Moser Engineering to replace my 14 year old axle shafts, or maybe even a full-floater conversion from Warn.

The following is not a manual on how to install either the Ox locker, nor is it a manual on how to set axle gears correctly. This write-up is simply a little overview about what is involved in installing an Ox locker, setting gears, and some other procedures that are required for an axle rebuild. Not covered in this article are any of the axle bearing replacement procedures, for example.

Building an axle requires quite a financial commitment, even though the axle itself my have been a good deal. I paid $95 for a complete D44 at a local yard. This was a good start, but by the time all was said and done, far over $1000 were spent. $750 were for the Ox alone (before shipping). Tools not included. If the work is done in the home shop, considerable amounts of time should be allowed for this as well.

A poor man's shop (in other words: yes, it can be done on the back porch!) :-)

Left: the original carrier.
Right: the new Ox carrier (with new ring gear already installed.)
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Here again the is Ox carrier with ring gear. Above the ring gear, the ring to engage and disengage the differential is visible. The shift fork (in cover) slides into the groove of this ring (very tight tolerances here!)
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This is the big cover. This cover is machined out of one heck of a big block of steel. It is strong enough, I would say, to withstand some of the hardest impacts imaginable.
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This is the cover seen from the inside. The big shift fork is clearly visible.
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A little grinding is involved to clear the shift fork. This is very important, otherwise the shift fork will not be able to travel freely. The Ox instructions are excellent in explaining exactly what to do and how to do it.
If you have this part of the installation done at a shop (i.e. gears), make sure the shop understands that this grinding part is extremely important.
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Those are the shims required to install the new differential into the axle housing. A micrometer is needed to measure the shims. Luckily, the shims are easy to measure, since the typical steps of shim thickness is .003", .005", .010", and also .030" (in this case the shim set is for the Dana 44 differential bearings). Other shims are for the pinion (behind the race) and pinion preload (that is: no crush sleeve in the D44).
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Here I hone out an extra set of new differential bearings to make the shimming easier. The manual's method did not entirely convince me, so I preferred this method. I honed out those bearings so they can be manually, i.e. without tools, installed and removed. That method proved to be not so good, since the shims where not tight enough behind the bearings. If I were to do this again, I would  hone out the bearings as shown here, but less, so that they are still somewhat tight and require a remover tool (bearing splitter' or 'bearing remover') to be used when removing them. This may be a bit more time consuming, but the result would be far more reliable. However, with a strong bearing remover, I was able to remove stock, non-honed Dana 44 differential bearings without damage (unlike those of a Dana 35).
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Now it is time to reduce the outer diameter of the rear pinion bearing race. The Dana 44's pinion depth shims are placed behind this bearing race (in the housing). To remove the shims without getting out heavy equipment each time, I decided that an extra race sanded down enough to slide in and out of the housing would be of great help. This indeed was of great help. The front pinion bearing still needs to be removed every time a pinion depth shim adjustment is required, but this bearing seems to come off fairly easily without a puller. Not too hard to do, but simply a bit time consuming.
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This picture shows the two pinion gears next to each other. The larger one is the 3.55 and the smaller one the new 4.56. There are no shims behind the rear pinion bearing on the D44. Other differentials use the rear pinion bearing to adjust pinion depth. All three Jeep Cherokee Dana differentials are somewhat different in this regard (D35, D44, and D30).
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Here the ring and pinion are installed using the previously honed-out differential bearings and sanded-down rear pinion bearing cup. A first set of shims were used based on measurements and previously used shims plus/minus whatever the new pinion indicated. This is the part where the manual is required and due to the amount of explaining required to set the gears, I will not get into more detail on this procedure here. Anyway, the picture shows a first test using yellow marker grease. The wear pattern is off (should be centered. Check your manual). Now the differential and possibly pinion have to be removed and shims have to be added or subtracted. This could cause a change in backlash, and therefore backlash may need to be readjusted as well.
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Once the gears are set (wear pattern and backlash ok), then the pinion bearing preload needs to be set. In the case of this D44 this is achieved using shims (whereas the D35 is using the infamous crush sleeve). A dial type in.lbs torque wrench is needed for this. It may take several attempts to get the preload set correctly.
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The Ox locker installed in the axle housing.
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Now it's time to do a final check. Another wear pattern is required and also another backlash measurement. I had to readjust my 'final' adjustments a few more times. Even though I had it all within specifications after another try, I kept adjusting backlash until I had it at the lowest end of the tolerance spectrum, which is from .005" to .009" in the case of the Dana 44. I eventually got the backlash set to .0053", which should be excellent for future wear.
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The reason why my initial settings were off after the 'final' installation was because of the honed-out differential bearings that I used. These temporary bearings did not compress the shims enough. The shims get kinked a little bit but only under full pressure. Not a big issue, but it made it necessary to remove the final bearings a few more times.
The arrow to the upper right in the picture points to the kink in the shims.
The arrow further to the left points to the differential. Here a slight chamfer. This is identical to the original carrier and is not a particularity of the Ox differential.
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This set-up shows the tools required to pull the differential bearings off without damaging them. A big bearing remover and a sturdy T-bar. I am using a big socket between the T-bar push rod and differential. The socket has to be small enough to clear the inner bearing race, but also big enough to sit on the rim of the differential.
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Now it is time to focus attention on the cable assembly. A few comments regarding this cable: This a a very strong assembly, far stronger than a parking brake cable assembly, for example. Strength is a good thing, of course, but it also comes with some inconveniencies. Routing the cable is not easy. Tight turns are impossible. It requires several feet to get a 90 degree turn! The installation instructions make this very clear. Routing is ultimately very similar to a parking brake line, however.
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The first step in installing the cable and shifter assembly is a test install. This helps a lot to better understand the interrelations of the different variables involved in this. The adjustments of this assembly reminded me a bit of setting gears. A small amount can make quite a bit of difference. Plenty of time should be allowed for this step. A proper alignment is critical for the proper operation of the Ox. A misaligned shifting mechanism could cause damage, but only if engaged. The default ('failure position') is in the disengaged position and in the worst case, the differential acts just like any other open differential.
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Again the test set-up. Cover, instructions, and shifter block.
Tip: If you plan on having a shop install this locker, be warned that the part of the cable/shifter installation is time-consuming if done correctly. Allow for this time, and if necessary, alert the shop to this fact --since the Ox is still fairly new. If not, you risk that a shop takes shortcuts to make up for the misestimated time!
As an alternative, you could have only the gears and locker installed. With the original cover installed (and gear lube in the diff!). You can drive home (open diff is the default for the Ox) and do the rest on your own time, provided you have a good chunk of time at your disposal. This would also be good, since the cable/shifter mechanism might be the most probable cause for failure on the trail. Familiarity with this mechanism will be very valuable if it in fact should be the cause of trouble out there, plus --it's fun to learn all you can about this luxurious locking device!
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Now to the part that I dreaded the most: where to place the shifter?
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I quickly realized that my original location --the little coin tray-- would not work. I wanted to use the coin tray but the shifter block, i.e. the stiff cable would not allow for this. The Ox instructions make this clear too. The shifter block and cable assembly need to be installed in a location where the cable can run straight for at least 16". Now, find such a location in a Cherokee! After looking at many possibilities, I decided to install it on the center console next to the parking brake (as shown). After all, the shifter also should be within comfortable reach. This location worked fine, and perhaps with some finessing, some day another shifter will fit in front of this one for a front Ox. The center console's passenger side ridge has the air duct for the rear compartment in it and would not allow for mounting the shifter block without losing the duct. This is not a big deal, since the duct has little to offer, but in cold climates, the large volume of air in the back will then take even longer to warm up.
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The black inset removed from the center console. A cut for the shifter (to 'sink' it, --shown in some of the following images). I moved the shifter as far back as possible without compromising operator comfort. This position might allow for just enough room to eventually add another shifter assembly approximately 2" to 3" in front of it for a front axle Ox locker.
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Here a test install to see if it still clears my GPS setup without interference.
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A first test install of the shifter in its final location on the center console. The cable goes underneath the console unobstructed and straight back.
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The axle and center console are now ready to be installed!
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The axle finally goes under the rig (using the old cover for protection).
Up to this point, a shop could do the work (gear setting/locker). The rest, below, could be done by any gifted home mechanic with some time to spare. Have the shop reinstall the OEM cover (like in this picture) and the differential filled up with some real cheap diff lube.
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Now the shifter cable is installed in the Ox cover.
If a shop did the work to this point, remove the OEM cover and drain the diff lube. Then follow the Ox instructions for the rest. The remainder of this write-up would be the work ahead of you if you decide to go the shop/home route and doing the cable/shifter installation yourself.
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Here the center console is removed. A sizeable oblong hole is required to route the cable through the sheet metal at such a shallow angle. In this picture, the cable end is pointing to the oval shaped hole that I cut for this purpose. I opted for the oval/oblong shape to allow the cable to travel through the sheet metal in a shallow angle to avoid unnecessary kinking or rupturing of the cable housing.
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This is the approximate position of the cable underneath the center console. The arrow is pointing to the hole.
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The cable shown from underneath. I added some extra protection to the cable, primarily to quickly identify chafing, etc. during  the frequent future optical inspections. (Red arrows pointing to Ox cable).
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The D44 is in, but the original drive shaft is too long and a new drive shaft is ordered. When testing for angles, I also noticed that I was extremely close to max things out (in spite of a YJ-style yoke) and decided to add a slip yoke conversion kit.
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The center console is reinstalled with the shifter in it.
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Detail view of the shifter's final position. A tight fit, but the only way I could think of. Remember that the cable needs a long straight distance from the shifter's location. Not exactly easy to accomplish in a vehicle that uses almost every square inch of interior room for something, --especially if already modified with all sorts of gauges, switches, navigation and communication equipment! Looking at my '97 XJ with the new interior, this might be entirely different.
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Summary:
Overall, this was not as difficult as I first thought. I had some expenditures for some new tools to do the differential work. A press is required, but the $109 12-ton press from Harbor Freight was plenty sufficient. The axle shaft bearings were replaced with this press as well, but the press bracket was temporarily moved down to the last bolt hole where the foot assembly usually is placed. This could be facilitated with a more permanent solution by either purchasing a second bracket and bolting it in for good instead of the foot assembly, or simply welding another bracket that could be used as the press's foot.

Another tool of importance is a big gear splitter, aka. bearing puller (shown in one of the pictures above). The local tool specialty shop should have a variety of those. I opted for a fairly big one, simply because I didn't want to risk breaking anything. The splitter was around $80 and a strong T-bar for it about $50, the grade-5 bolts for the T-bar, about $2 ea. This splitter actually allowed me to pull the retainer ring off the axle shaft. (--cold!-- not pre-heated, no drilling and breaking).

Another investment was in a good inch-pound dial-type torque wrench (shown in one of the pics above). This torque wrench is needed to set the correct pinion preload on a variety of axles. It wasn't exactly cheap ($130-$160), but definitely worth the money. Don't be surprised if you across this tool in other articles.

To set the gears, a micrometer is required to measure the shims. To measure backlash, a dial-type micrometer with a magnetic base is recommended. Neither of those two tools were too expensive at the local tool supplier, and --again-- a worthwhile investment. The micrometer can come in handy at many instances. The dial-type micrometer could also be used to measure run-out at drive shafts, etc., etc.

Other than that, a fairly well equipped shop should have most of the tools already. A factory service manual is basically mandatory for this sort of work. It contains all the critical measurements. I was lucky that mine ('89) covered the Dana 44. I am not sure which manuals have the chapter covering the Dana 44.

Overall, the entire install went amazingly smooth. The only slight surprise was that I basically could no longer squeeze by with the old rear (although, custom) drive shaft and a slip yoke kit now seemed necessary to avoid costly damage in the future. The Dana 44 housing is longer than the D35 housing. Angles were getting too steep in my case (and my level of comfort). I didn't want to risk binding u-joints, since this inevitably would not only damage the transfer case but also could damage the pinion bearings which in turn would contaminate the differential lube with metal shavings. That would then ultimately be hard to that high-dollar differential and possibly ruining it in the long run. In a word, this type of potential chain reaction wasn't what I was willing to risk.

I really was happy in regards to the overall engineering of this Ox locker and also was very pleased with the high-end machining and quality of this piece of equipment. I often spent time playing with all the pieces, slowing me down during the install. But, that's what this is all about anyway, isn't it?

After having the chance to finally test the Ox in the mud under some fairly demanding off-road conditions, I was pleased with its performance. Not too much differently (off-road) from my previous Lock Right, but the ability to unlock the rear differential for on-road travel was the true gain. This vehicle is still in use as a daily driver with occasional off-road use (but obviously the off-road miles are a small fraction compared to the on-road miles traveled).

The shifter position proved to be a great choice! With the right arm comfortably rested on the center console, the locker can be engaged "out of the wrist". It takes a little time to get used to this type of manual locker but with a little wiggle in the steering wheel while pushing the locker shifter, engagement and disengagement of the locker was always a smooth and quick process. It is best to engage the locker before diving into mud, etc., because once stuck, it might be more difficult to engage the locker.

This type of cable locker is nice because of the feedback the driver receives through the cable mechanism. You know if the locker engaged properly or not. I never owned an ARB (air pressure assisted locker) equipped vehicle, but I am sure that pushing a button (even though this really slick) does not tell the driver much about how and if the locker engaged. This feedback is also missing in the early G-wagen (Mercedes G) with its "stubbies" (i.e. the original hydraulic assisted manual lockers). Later Gs received the electric assisted lockers which made the engagement easier. The early Gs required the driver to lean forward and then pull decisively on the "stubby". I didn't like that too much, and must say that my Ox-equipped XJ is more comfortable, --even if this may be the only instance where this is the case. :-) And again, this is the only other manual locker I have experienced and can compare it to. As said, I never had a chance to drive an ARB equipped vehicle, nor one of the Toyotas with electric lockers. The Ox has its advantages, but the additional "mechanics" also makes it more vulnerable to damage when compared to a Detroit locker. But for a rig that still sees a lot of on-road travel, this is possibly the best choice, in spite of its demanding price tag.
©Copyright 2001 Andreas Ritterbusch
All Rights reserved.
Photos: Andreas Ritterbusch

 

[MADXJ]