Many of us JK drivers find it particularly easy to cram in some big tires with the extra large wheel wells offered on the new Jeep.  With only a few inches of lift 37’s are no problem.  We are even starting to see a lot of 39’s and 40’s stuffed under JK’s. However, they are mounted to the factory Dana 44’s.  Yes, the new Rubicon 44’s are a pretty stout package compared to their predecessors but there is only so much a 44 can take. It’s only a matter of time before you’ll either snap a factory shaft or bend the somewhat  weak axle tubes.  After already breaking an axle, we wanted to toughen up our axles before snapping another one.

There are several shaft upgrade options on the market for the JK axles and we wanted to make sure that the strongest possible material made it into ours.  No hardened Gumby and Pokey clay material would be enough for our 37’s and driving style so we called National Drivetrain (www.nationaldrivetrain.com) and spoke with them about their new chromoly axle shafts for the JK.  They just announced their new line of JK shafts called TEN Factory and each consist of high tensile strength material.  For the front, each axle is made from 4340 chromoly and then heat treated twice, producing a product that is up to 30% stronger.  An exclusive 10-Year warranty is standard and the shafts come completely assembled with inner and outer shafts, u-joints and full circle clip .  

A nice feature is the fully assembled front 4340 chromoly axles come ready for install.

The full circle clips are especially important as we have encountered several JK’s on the trail with a u-joint cap that has failed and popped out of the axle ears due to standard c-clips, allowing the ears to be broken clean off.  The 5-760X u-joints that we got from National Drivetrain are also very impressive compared to our stock units. They are a BIG step up from the 297’s that Dana ships with each Rubicon 44!

Here you can see the full circle clips installed on the u-joints, making them much less prone to breakage.

The rear axles are equally as impressive and National Drivetrain offers two options:   4140 chromoly and 1541H high-strength rear axle kits.  For those that want a slightly stronger material than stock, that will provide excellent durability, 1541H is offered and won’t break the bank.  We feel that the 1541H rear kit would be a great choice for one who is running 35-inch tires or 37’s with a light right foot and moderate wheeling trends.  For the ultimate in strength, choose the 4140 chromoly as we did.  This high-strength alloy is also double heat-treated to produce heavy-duty axles that are up to 35% stronger over stock.  Of course, they too carry the exclusive 10-Year warranty and come complete with both passenger and driver side shafts, bearings, seals and wheel studs.

The rear axles also come fully assembled and ready to slide in. We opted for the 4130 chromoly that are 35% stronger than the stock units.

With our chromo shafts ready to go, we felt that it was finally time to upgrade our gears while we had our diffs opened up.  While many JK owners are choosing a 5.13 gear ratio to compensate for the lack of power and torque provided by the 3.8 Liter mini van engine, we took a slightly different route.  Strength is our number one priority with this JK project and by looking at the pinion head on the 5.13 gear set, it was decided that we felt more confident with a set of 4.88’s.  If we were running Dana 60’s, we’d be fine with the 5.13’s, however, a Dana 44 pinion head seems a bit small for our big JK.  The 4.88’s provide plenty of power, allow us to cruise the highways in overdrive and our rpm’s stay low enough to net us some pretty impressive fuel economy numbers.  With the 6 speed manual tranny and a 4:1 transfer case, we feel that 4.88’s are just right for any JK owner.

Our new 4.88 pinion gear are pictured here next to the factory 4.10 pinion.  The 5.13 pinion was just too small for our comfort level so we stuck with 4.88's for maximum strength.

The decision on who installs your ring and pinion is as critical as who manufactured them.  One small mistake by a careless technician can mean the demise of your new gears in a matter of hours.   Our Superior Gear ring and pinion set (also from National Drivetrain) was taken to our most trusted shop in all of Colorado, 4 Wheel Parts Performance Centers of Westminster, CO.  Mike Abbiati, Store Manager, put his master Technician Steve Husmann on the job and assured us, we, nor our gears, would be singing the blues after they were installed.  Husmann has done many JK gear installs and was very familiar with the JK locker sensors that have been causing problems for the lesser experienced shop technician.  His thoroughness, experience and overall know how was reassuring, even as we flashed our camera in his face.  4 Wheel Parts Performance Center, Westminster has always come through for us in the past and we wouldn’t let any other shop around get under our JK. 

The locker mechanism is vulnerable to breakage during a gear install but the 4Wheel Parts Performance Center in Westminster, Colorado knows their way around JK's and handled the install with ease.

Our new shafts and gears were one of the best improvements we’ve made to the Jeep so far.  The Superior gears provide a great combination of highway power and off-road torque, while our new super strong National Drivetrain TEN Factory Chromoly axle shafts give us the confidence that we won’t break in the back country.  Stay tuned, as our next mission is to strengthen our Dana 44 housings around our new super stout shafts as Mt. Logan 4x4 will give our 44 housings Dana 60 like strength.

The 4Wheel Parts Performance Center in Westminster, Colorado knows JK's well and performed a flawless install on our 4.88 Superior gears.

Sources:
4Wheel Parts Wholesalers
7001 Federal Blvd
Westminster, CO 80030
303-430-9300
www.4wheelparts.com

National Drivetrain, Inc.
734 W. 43rd Street
Chicago, IL 60609
866-427-0080
www.nationaldrivetrain.com