Enjoy the many detailed, traditional ‘Q&A’ exchanges in these article columns…’Q & A’ has now moved to open, interactive forum discussions. Visit the forums, you’ll want to join—for free!
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AW4 Automatic Transmission Interchange
From: Wayman M.
Sent: Sunday, June 24, 2012 6:39 PM
To: 4WD Mechanix Magazine
Subject: AW4 year changes?
Hello, Moses…1997 XJ 4.0L, NP231; I’m shopping for a new AW4 and found one on Amazon, but they list it for only 1994-1996. Why those specific years? I thought the XJ AW4 was only changed in 1991 to the 23 spline output then it was the same until 2001. Is it a different TCU? I been told that the ’98 has a some different connectors.
Part# S-4810179 keeps coming up for the ’91 and later AW4’s.
Wayman…Chrysler’s Mopar Reman program only offers and groups the 1998-2000 model AW4 units…nothing offered either before or after, although 2001 may be a part of this group.
NAXJA has a loyal forum, and I found this entry:
According to the source, you can use a 1990.5 through 1997 unit with just a change in the wiring plug. (1987-90 will even fit with mods mentioned.) Based on this source, I would avoid the 1998-2001 units completely.
Read down through the forum threads. They sound like a lot of homework done on your behalf, Wayman!
Let me know how this turns out,
Ticks in an XJ Cherokee
Q-1. From: James B.
Sent: Monday, June 13, 2011 3:37 PM
To: 4WD Mechanix Magazine
Subject: Driveline noise
Thanks for fielding my earlier question. I have a 2001 Cherokee Sport that I enjoy wheeling with and I also use as my daily driver. Recently I have noticed a ticking sound coming from the front of my Jeep. It makes an audible tick, tick, tick, tick, when backing up, driving forward as well as when I turn. I can’t tell if it stops as I accelerate or if it is just drowned out by the engine noise as I drive faster. I really think it is still making the noise even though I can’t hear it over the road and engine noise.
I have a Richmond lockright unit in the Dana 30 diff. so that is where I started my troubleshooting. I lifted the front of the jeep and disassembled and inspected the front axle, pulled wheels, brakes, axles, opened up the diff. and installed a new spring and pin kit in the lockright and inspected the unit for wear. Everything internally looked good. I inspected everything except the unit bearings, although they didn’t seem to have any slack in them when I removed the wheels. After putting it all back together I was expecting the issue to be gone. But there it was tick, tick, tick, tick. As loud as ever!
Now, having done all of that is there something I’m not checking? Like I said the ticking sounds like it is right at the front wheel /axle if I stick my head out the window as I creep forward or reverse. I am at a loss. Can this ticking be from the unit bearings, Transfer case, tranny???? Please let me know if you have a solution to my problem as I said this XJ is my daily driver and is near and dear to my heart. I’d hate to have to take her out back and put her down!!!
A-1. Hi, James…Your noise is frustrating, and you have covered some in-depth possibilities! This is an instance where a sonic/audible tester would be helpful. I have such a device with multiple channels that can actually be used as you drive the Jeep. You can hook up sensor pickups at various locations on the front end and axle housing, and by deducing the amplitude of the ticking noise at each channel, you can narrow down the search.
Dealerships often have this device; mine was part of a Mopar dealership diagnostic tools package. If this sounds cost prohibitive, there is the traditional option of safely planting the vehicle off the floor on four secure safety stands; place two stands beneath each beam axle. With the transfer case in low range to minimize rpm at the wheels, operate the vehicle in low gear, using extreme caution to prevent risk of personal injury. Avoid any physical contact with the wheels/tires. (Note: You can run this test with the wheels and tires removed; securely attach wheel nuts on the wheel studs to prevent the rear brake drums or the rotors from separating.)
Listen carefully to pinpoint the trouble spot. Since the noise is apparent with any rotation of the front wheels, you should have no trouble isolating the source—unless the noise occurs only with weight on the front wheels and hub bearings…In that case, the tick is the unit bearing hubs, especially if they are original and the Cherokee has oversized tires with wide wheels and shallow backspacing. (See the article on unit bearing replacement at the magazine website’s XJ Cherokee Workshop.)
An additional step is to remove the front driveshaft and drive the vehicle. If the noise disappears, you know it is either front driveline or transfer case related. A bad U-joint (either driveline or axle shaft joint) can cause a “ticking” noise.
I want to know what you discover. Please use extreme caution if running the vehicle on secure stands. Be sure the stands have solid four-point bases and rate at least one-ton per stand. I use Walker ratchet lock stands from “the day” that have a 5,000 pound rating per stand. These stands have safe saddles that securely support the axle tubes. If you need an example of safe stands, let me know. I’ll send a link.
Q-2. From: James B.
Sent: Friday, November 04, 2011 8:12 AM
To: 4WD Q & A
Subject: RE: Driveline noise
First I would like to say Thank you to Moses and 4WD Q&A for all of the sound advice. After reviewing my options and my budget, I decided to attack this thing starting with the cheapest parts, the U joints. Since they were still the factory U joints, and I could pick up all 3, axle and front drive shaft, for a lot less than the unit bearings this was the most cost effective place to start. Pounding out the axle end joints was a bear, but the drive shaft joint had U bolt type straps holding it in place, which made for easy removal. Once I installed the new U joints and put it all back together I drove it around the block and what do you know?! Ticking sound completely gone! Even after putting on my 32” Super Swampers, the annoying tick wasn’t there. I guess it was luck that I found the issue right away but my pocket book is happy none the less! I am excited to say that last weekend we got a chance to take the old XJ for a weekend retreat at Barnwell Mountain OHV park here in East Texas where she performed flawlessly on every trail I pointed it at. We had a blast and were able to keep up with the big boys all weekend long. I just wanted to say thanks again Moses for the insight and see y’all on the trail!
A-2. Great job, James! Glad the XJ is trail worthy and fun to use…Enjoy it…
231 Transfer Cases: With or Without an SYE
From:4WD Q & A
Sent:Tuesday, April 05, 2011 8:45 AM
Subject:RE: NP231 T case
Hi, Jason…The overall length of a ’95-’96 XJ 231J transfer case should be the same. Note the rear driveshaft type. Does your 1996 model have a slip-yoke-eliminator (SYE) kit? This would shorten the extension housing and also has a flanged U-joint yoke that accepts a single Cardan (cross type Spicer) U-joint. If the ’95 transfer case does not have this conversion, it will have a longer extension housing to work with a sliding “slip coupler/yoke” driveline.
See whether the ’95 231 is for a slip yoke driveshaft (which would be stock). Note whether your 1996 unit has a slip yoke eliminator kit and a CV (double Cardan) rear driveline. If you do not have a slip yoke rear driveshaft, an SYE kit has been installed. You would have to install an SYE kit on the ’95 transfer case to use your SYE driveshaft.
Let me know what you find…
From: Jason D.
Sent: Monday, April 04, 2011 10:23 PM
To: 4WD Mechanix Magazine
Subject: NP231 T case
I have a 96 XJ with a NP231J and the chain is loose inside the transfer case. I picked up a used, NP231J from a 95 XJ. I noticed the housing at the rear of the case is different. The one on the 95 tcase has an extended housing. The one on my 96 tcase doesn’t.
Can I still use this NP231J?
Hi, Jason, glad you found the right transfer case…High range shifting should be relatively easy if there is no interference. This is a simple, “shift-on-the-fly” approach that allows shifting between 2WD/4WD high range positions without difficulty and at any speed. I back out of the throttle momentarily when affecting this shift to relieve load on the shift components.
Low range requires stopping the vehicle, or a near stop, to affect the shift. Otherwise, there will be gear clash. It is not uncommon to have gear bind or misalignment of shifting components when making this shift to low range. Avoid placing the transfer case in Neutral when making this shift. With the vehicle stopped, move the shifter right through the neutral position, quickly, and into low range 4WD.
Begin by stopping the vehicle and either placing the transmission in neutral or depressing the clutch (if a manual transmission). Shift the transfer case right through the neutral position to 4WD low range. If there is binding or clash, stop the process. If you accidentally get stuck in the transfer case’s neutral position, shut off the engine to prevent gear clash. (Idling the transmission in neutral allows the transmission’s output shaft to rotate; if the transfer case is in neutral, you will not be able to engage the other transfer case positions while the transmission’s output shaft is rotating.)
Try these techniques, and if the problem persists, we can discuss the issue more. As a given, check for any binding or rust inhibition in the linkage…
From: Jason D.
Sent: Sunday, April 17, 2011 12:43 PM
To: 4WD Mechanix Magazine
Subject: RE: NP231 T case
Thnx for the reply. I was lucky enough to find another NP231 out of a ’96 the next day. It has the same tailhousing. I installed it, and it works. Now my problem is
when shifting into 4high or low you have to ram it into gear. The shifting mechanism under the vehicle is rusty. Could that be the problem?
XJ Cherokee with Continuous Vibes
Hi, Moses…I have a 1998 Jeep Cherokee Sport 4WD 4.0L, automatic with 121,000 miles. The vehicle has an 8.25″ Chrysler rear axle without ABS. The transfer case is a New Process 231J. I purchased the Jeep in 2004 at 91,000 miles. Since the beginning, the Jeep has a DEEP DRONE that starts between 60 and 70 MPH. It is VERY annoying to say the least! I have had the rear drive shaft replaced with the upgraded Mopar shaft with rubber damper. I had the spacer kit installed per Mopar TSB 980327 to drop the transfer case and change the rear driveshaft angle. I have had the front and rear differentials rebuilt, replaced the front hub assemblies and replaced the engine mounts with genuine Mopar units. I changed the tires to a set of Michelin ‘LTX’ P225/75‐15 and Goodyear Forteras. None of this makes a difference…I have replaced the rims with brand new Jeep 5‐spokes. I had the front Cardan joint replaced by a local machine shop, replaced the ATF fluid in the transfer case with synthetic ATF, and the drone continues. I have not had any work done to the automatic transmission or the transfer case beyond fluid and filters.
The Jeep is 100% stock except for the drive shaft and spacer kit. The noise/drone was present prior to all the work listed and prior to the tire brand changes. The vehicle currently has Hercules P225/75‐15 Terra Trac SUV tires because of their very non‐aggressive tread. My Jeep has never been drone or vibration free in the four years I have owned it. If your shop can help, I can
drive the Jeep to your facility for repairs if advised. Thanks!—Joel Z.
Wow, you have incredible commitment to this XJ, Joel! As you know, I have a ’99 XJ project vehicle that appears throughout the website and this magazine. The XJ provides an ongoing test‐bed for the XJ Cherokee owners’ issues…To begin, any tire balance issues usually occur between 45‐55 mph, normally not pronounced below that speed or above 65 mph unless there is a belt separation or more severe out‐of‐round condition. Driveline vibrations generally occur gradually, increasing in intensity with driveline rpm (equivalent to road speed). Since driveline angles are usually correct from the factory, it’s interesting that Jeep issued this TSB request for a transfer case drop on a stock‐height vehicle—without a lift kit or even the ‘Up Country’ factory off‐road package.
With the part‐time 4WD, ‘231’ transfer case, you can disconnect torque to the front driveline in 2WD high range. Your vibration sounds prominent in 2WD and presumably 4WD high range as well, although you may not have tested 4WD high range on a loose traction surface at 65‐70 mph speed. There is the possibility of a transfer case shaft, sprocket or planetary assembly imbalance, perhaps there’s an engine or powertrain harmonic imbalance.
At left is stock ’99 XJ Cherokee 231 transfer case with original rear driveline that Joel describes. U‐joints are single Cardan at each end of the driveshaft. Illustration at right is a heavy‐duty, aftermarket Advance Adapters’ slip yoke eliminator (“SYE”) output with a CV conversion joint, commonly used with suspension lift kits.
However, these would be long shots, the last items to consider. I would start with driveline issues. To isolate the front driveline, try removing the front driveshaft assembly and driving the vehicle in 2WD mode to speed. If the drone disappears, there is a clear relationship between the front driveline and the problem. If the drone continues, since you have tried two rear drivelines, I would carefully measure the rear driveshaft joint angles to see if they meet specification.
The joint angle at the front (slip yoke) and rear (pinion) should cancel each other on a single Cardan, cross‐type U‐joint arrangement. At the front driveline, the transfer case end uses a self‐cancelling double Cardan joint. The single Cardan front joint angle is relative to the front axle’s caster angle. By self‐cancelling, the double‐Cardan “CV” (constant velocity) joint helps eliminate a variety of vibration issues.
Measured angles at each joint of a double Cardan CV are approximately half those of a single Cardan joint. CVs are popular and work well on long front drivelines with a gradual slope and considerable front axle caster angle. If the rear driveline’s joint angles do not cancel at 1‐degree or less— the less, the better—you have a problem.
Maximum driveshaft joint operating angle should be less than 3‐degrees. Minimum operating angles should be ½‐degree. If the driveline U‐joint angles are less than ½‐degree (essentially straight), the needle roller bearings in the joint will not move sufficiently. Premature bearing failure will take place from this lack of movement and poor distribution of lubricant.
Caution: A U‐joint often fails when the pinion has been rotated upward on a lifted truck with a CV rear driveline. If the single Cardan rear joint has a zero‐degree operating angle, the needle bearings will wear rapidly. I like to see approximately 1‐1/2 degrees of angle on that single joint —with the vehicle loaded normally and each loaded axle perched on safety stands.
The factory TSB (service bulletin) assumes that the transfer case needs to be dropped to reduce driveline angle and change the U‐joint cancellation pattern. On your XJ, the rear driveline’s front joint now has less angle than before the drop. It is still possible that the angles are not correctly cancelling each other. If so, the next move would be to place correction wedge shims between the rear axle’s spring pads and the leaf spring stack. This will rotate the pinion upward or downward to set the correct U‐joint angle.
When taking measurements of the U‐joints, I like the vehicle to be at simulated road height. This means that the vehicle is either on four stands placed squarely at the front and rear axles, or the vehicle sets level on a drive‐on ramp lift. Our old shop had an asymmetrical side arm lift, so I placed a pair of 2‐ton tripod stands at each axle, as directly beneath each spring point as possible. I rested the vehicle on stands to simulate an on‐the‐ground load.
For driveline angle checks and lift kit installations, I raised the vehicle on our side‐arm lift and set 2‐ton (each) tripod stands carefully beneath each axle. I then lowered the hoist enough to fully load the stands, leaving the lift arms in place for safety. A drive‐on ramp hoist will also work well for driveline checks.
If you have no hoist and can get safely beneath the vehicle on the ground, that works, too—or four high‐quality chassis jack stands can be used, a pair at each axle, if you can safely get beneath the vehicle while
it sets on these stands. With the vehicle level and its normal highway or trail running load on each spring, you can now measure the driveline angles.
The Jeep factory manuals prioritize proper driveline angle over caster. Here, I disagree. Since the front driveline is a CV type and long, and since your vehicle is stock height and not lifted, I believe that it is wiser to concentrate on adequate caster angle. Lacking sufficient ‘positive’ caster angle, XJ Cherokees often experience the so‐called “death wobble,” a lay term for the time‐honored, classic kingpin shimmy.
Having operated the alignment rack at a GMC truck dealership during the beam axle era, I draw attention to the XJ Cherokee’s factory‐recommended front axle caster angle: 6.5‐degrees of positive caster for manual transmission models and a full 8.0‐degrees of positive caster for automatic transmission models. This is considerable caster and necessary to prevent shimmy.
From my experience around new truck warranty vibration issues, I would not drop below the XJ’s recommended 6.5 degrees positive caster to adjust a front driveline U‐joint angle. With a CV joint at one end of the front driveline and a relatively long driveshaft, the correct caster angle should provide an acceptable driveline angle.
Note: If the vehicle has been dramatically lifted, that would be a different situation.
Jeep engineering attempted to counter both driveline vibration and caster issues like kingpin shimmy. (The steering damper helps some.) Angles were apparently a delicate balance with the XJ Cherokee’s vehicle dynamics. Early on, the aftermarket suspension lift kit manufacturers discovered that changing the driveline angles creates problems. Their solution was the slip‐yoke eliminator and a CV‐driveline that could reduce joint angles and help counter the driveline vibration.
Note: The XJ Cherokee has a unitized body with an inherently high sensitivity to NVH: noise, vibration and harshness.
Slip Yoke Eliminator (SYE) kits have become a mainstay for Jeep aftermarket suspension lifts. Two major changes occur here: 1) the shorter transfer case tailshaft allows for a longer rear driveline and 2) the aftermarket CV‐type rear driveline has two joints that self‐cancel. The axle pinion end of the rear driveshaft uses a single Cardan U‐joint. That joint’s angle can be radically reduced by rotating the axle’s pinion flange upward.
Comment: When a driveline is lengthened with no change to the transfer case, chassis height or joint design (visualize the side view), the shaft can handle higher torque loads. This is due to the reduction in U‐joint angles. Less angle, less load, less tendency to vibrate!
Joel, if everything checks okay, including the joint angles and the balance on your rear driveline, you might consider an SYE kit with a custom CV rear driveline. Given that your XJ is at stock height, this would surely lend itself to smoother driveline operation. Use my formula for the rear, single Cardan joint’s angle when tilting the pinion: 1.5 degrees or so, no less than 0.5 degrees—at loaded, curb vehicle height.
As a final note, with a CV driveline and fixed yoke at the back of the transfer case, you could remove the rear driveline (without
any oil pouring out) for testing the vehicle. With the transfer case in 4WD High and the rear driveline removed, you could drive in front‐wheel drive to speed (on a straight road) and see if any driveline harmonic vibration or droning remains.
This is a CV driveline conversion on an XJ Cherokee. The SYE kit has been fitted to transfer case output. A SYE uses a longer driveline with a self‐cancelling, double‐Cardan CV joint at the front. The rear, single U‐joint’s angle is controlled by the tilt of the rear axle pinion. Note that this axle is at full suspension drop, not at loaded, static curb height. The pinion/Ujoint angle is greater than at curb height.
If droning still persists, final possibilities would be the internal components of the transfer case, an engine and powertrain harmonic imbalance or an axle differential carrier and ring gear that run out‐of‐center. Each of these would be less likely prospects, although strange things do occur—like an imbalanced flexplate, defective crankshaft or damper, or a flawed torque converter.
XJ Cherokee Undergoing Serious Changes!
My wife and I purchased our XJ Cherokee new. At 100K miles, after years of patiently waiting, I have “inherited” the XJ and am about to make some changes. The right front axle shaft U‐joint is now squeaking rhythmically, the front axle pinion seal is leaking, and the other U‐joint at 100K miles can’t be in great shape. I have ordered the Superior Axle Dana 30 upgrade that you did on the project XJ Cherokee. I stayed with the 27‐spline shafts, opting to forego a locker in the front. The Chromoly axles and the beefy 760X U‐joints should be plenty strong for planned 31” tires and a mild lift. Of course, I had to get a pair of those cool looking red aluminum axle tube seals! The ARB diff cover will complete the front axle upgrade.
I know that the 30‐spline differentials are all the rage; the demand for the 27‐spline unit may drop to unacceptable levels. It would be nice to safeguard my investment in these lifetime guaranteed Superior axle shafts. I’ll keep tab on the availability of the 27‐spline ARB front locker. For now, though, I’m just installing a 30‐spline ARB Air Locker in the Dana 35 rear axle.
The XJ has a 242TC. Unless I blow it up, I am keeping it! I appreciate the full‐time 4WD mode on marginal weather days—we get many around here in the winter. My plan is to install the lift kit and take note of changes in driveline angles. With the adjustable lower control arms on the mild Skyjacker lift kit, I have some independent control of the caster angle and front pinion angle. I am confident that I can make these angles acceptable. That leaves the rear driveline angles in play.
The rear lift is only 2.5” over stock, according to Skyjacker. Maybe that works out to be okay or maybe the transfer case drop will bring the driveline angles back to an okay level. If it doesn’t work out, I will go with an SYE kit. As for the SYE conversion, the 242 does not have a commercial kit solution like the popular 231 units. All of these 242 SYE kits are some sort of ‘hack and tap’ approach. The MIT and Tom Woods solutions are the same: Cut off the existing tail shaft splines, re‐spline for a standard Dana yoke, and enlarge the tail housing for a new seal around the new yoke flange. The much maligned Rubicon Express
‘hack and tap’ takes a different course: Shorten the tail shaft but leave an inch or so of existing splines to accept a stainless steel flange they sell for $90. The problem with this kit is that they advertise you can do the cutting and tapping on the vehicle—maybe, but crudely. I would take the tail shaft out and have a machine shop do that cutting professionally. That leaves the shaft cutoff perfectly square.
I can get a Spicer built C‐V driveshaft for about $300, or I can get a custom‐built from Action Machine using American DOM tubing, all Spicer parts and balanced to 50% tighter tolerances than Spicer for $250. Action Machine would do the tail shaft machining for $60—so total cost for the mod is about $400. What do you think about this approach?—Jim J.
Jim, the biggest concern I have is heat treating. Actually, cutting off the original shaft (if the existing splines match the splines of the replacement yoke) could be okay. If done right, the cutting should not impact the heat treating. Keep in mind that shafts are typically 8620, 4130, 4340 or similar metallurgy plus case hardening. That hardening can vary in depth, tensile and Rockwell, depending upon the heat‐treating process. Below the case hardening, you’re dealing with softer and more machinable metal. If you were cutting new splines, heat‐treating would be essential.
Even in cutting off the OE shaft, there could be a HAZ (heat‐affected zone) that will denigrate the original heat‐treating, tensile and Rockwell (HRC). When the cut‐off is with the heat of a chop saw, that affected area would be considerable, and the spline hardening would deteriorate accordingly.
Stock 231 output shaft (left) compared to high quality new and heat treated Advance Adapters’ SYE replacement shaft for CV yoke. Retrofit SYE shaft (right) requires a virtual transfer case rebuild to install.
At the very least, cut the shaft to length with the least amount of sustained heat. (A liquid cooled band saw or lathe would be advisable if the shaft were out of the transfer case.) Drill the hole for the threads on center. Run a Rockwell test at the bottom of the drilled hole. If the tensile is sufficient for the threads to hold, tap the threads and use a premium Grade 8 bolt and a high tensile, thick hard washer to hold the yoke in place. Use a lock washer and apply Loctite 271 to clean threads. Tighten new hardware to recommended torque.
A recap of issues: If you do this hack and tap, keep heat to an absolute minimum; use a liquid‐cooled band saw or lathe with slower cutting speeds…As for threads, again beware that you’re drilling and tapping into softer metal, and the tensile strength of that threaded area is considerably lower than the hardened surfaces of the shaft and splines. Although the flange bolt should not have a great amount of end thrust (the rear CV drivelines have a splined coupler), the yoke does need to attach firmly. Tensile of the tapped threads is still a concern.
My approach would begin with normalizing the shaft (similar to annealing but not as intensive or costly). Then the cutting and machining could take place before re‐heat treating the shaft to proper depth and match with the original Rockwell hardness. I always test the Rc before normalizing and after final heat treat.
To illustrate the differences between a hardened and non‐hardened alloy material, consider 4340 steel: the annealed (nonhardened) 4340 is typically only 20 Rockwell C hardness; hardened, this same metal can be in the 55‐60‐plus Rc range for gear or shaft purposes. Even hardened, the tensile can range from 130‐200,000‐plus psi for 4340, depending upon the kind of heat‐treating method employed.
In an annealed state (similar to the material beneath the surface case hardening of a heat‐treated shaft), these metals have relatively low tensile. My concern is the tensile within the shaft at the drill‐and‐tap threads. To increase tensile at the threads, you would need to case‐harden (heat treat) the shaft after machining.
I understand your appreciation for the full‐time 4×4 mode in the 242 design. The 242 is common enough. There should be an aftermarket interest in an SYE conversion for these transfer cases.
Let me know what you do with your ‘242’ transfer case and the SYE approach if you go that route! I would like to know the Rockwell C (HRC) reading of the drilled thread bore in the stock shaft—prior to normalizing or additional heat treating.
Installed SYE kit shows shorter output length and yoke installed for CV joint on new rear driveline. This has become a popular conversion for lifted Jeep vehicles. Advance Adapters builds a high quality SYE kit that comes with all necessary parts, including a new housing, shaft, yoke and all related hardware. At this point, there is not a kit like this for the 242 transfer case.
As for the ARB 27‐spline differential for the Dana 30, it would be smart to watch ARB’s level of interest in continuing the 27‐spline front locker unit. 30‐spline is the buzz, and most installers now change to a 30‐spline and upgrade the axle shafts when doing the ARB installation. The application is usually for 33” or larger diameter tires.
Worth noting, you may never need a locked front axle with an ARB at the rear axle. You’ll find it very difficult to spin one front wheel when in 4WD low range with the torque bias being even front‐to‐rear. The Dana 30 at the front only receives 50% of the torque, so 27 splines with Superior’s axle shafts should be plenty—especially with 31” tires.