One of the most common breaking points on most off-road vehicles is the front axle assembly. Usually one of the last upgrades done to a vehicle, this doesn’t always get the attention it deserves and can have serious implications. There are lots of options for the Jeep JK Wrangler as it is currently the most modified off-road vehicle on the market. This guide is designed to provide more information on how and when to modify the JK’s front axle assembly.
Rubicon models come straight out of the gate with a stronger front end than non-Rubicon models. The JK Rubicon Dana 44 front assembly sports 8.5-inch ring gear versus the Dana 30’s 7.125-inch ring gear that is standard in JKs. The axle shaft diameter also increases and the spline count steps up to 32. Larger shafts and high spline counts equate to more strength.
The downfall to the Rubicon Dana 44 is the cast housing and the tubes. The cast housing has several weak spots that can fail even under moderate duress. The tube size is the same between the JK Dana 44 and the JK Dana 30 at 2.5-inch outside diameter with 0.25-inch thick wall tubing. JKs axles typically see more abuse than previous Dana 30 and 44 iterations. Larger wheelwell openings on JKs provide ample room for much larger tires without as much lift, making 35s and 37s (and larger) a much more common upgrade compared to TJ Wranglers.
What Should Be Under The Front End
Steps to upgrade axle assemblies in the JK are available but aren’t on the inexpensive side of your full build plan; though a broken axle, ring and pinion, housing, or any part of the assembly can ruin your day on the trail. With so many options on the market for front assemblies, wading through them can be a chore. Not being easy on the wallet adds to the stress of deciding which options to go with and why.
Currie Enterprises and Dynatrac have been building quality parts for a long time and can help guide you through what you need for your vehicle. Let’s run through what they offer. We’ll go alphabetically since they are both great companies; you can decide between features, price points, and options to see which you prefer.
Keep in mind, however, all the front axle assemblies in this guide can be used in a wide range of vehicles. For the purposes of this story, however, we are focusing on the highly-modified JK Wrangler.
A natural go-to for beefy axle assemblies is Currie Enterprises. Nearly 60 years ago, Frank Currie started fabricating and assembling rearends for personnel carriers, tugs, and other specialty vehicles. As the business grew, so did the family. Frank’s sons came onboard full time in the 1970s; it was all about hot rods and off-road vehicles from then on.
Currie Enterprises has been around the block, and the desert, a time or two. Over the years, the Currie Enterprises line up has evolved. Ford 9-inch housings were plentiful and worked great for many applications. Nowadays, there are even better offerings coming from the Southern California manufacturer. The sales people at Currie are trained to work with the customer and help determine their needs based on intended use.
To give you a head start, though, we’ll break down each unit and list the pros and cons. Here are the headlines:
- RockJock 44, a beefy replacement for a stock JK Wrangler front differential.
- F9 9-inch, a fabricated housing with a Ford 9-inch drop-in third member.
- RockJock III 60, a high pinion Dana 60 based differential that can take a beating.
- RockJock VXR 60, a hybrid between the RockJock 70 and 60 with massive 3.5-inch tubes.
- RockJock 70, a monster is for those with huge tires and a heavy right foot.
The RockJock 44 is designed for wheelers that need stronger than stock but in a friendlier budget range. The housing is designed to utilize stock JK Rubicon locker options as well as ring and pinion sets.
Stock knuckles, hubs, and brakes can be retained to help keep costs low. The RockJock 44, and all the other assemblies in this guide, can be used in Rubicon and non-Rubicon models.
Vehicles with a V8 engine conversion, 37-inch and taller tires and/or likes to mash the skinny pedal should be stepping up a notch or more.
The F9 9-inch is designed for desert application vehicles and high-speed, custom vehicles with a low center of gravity. The fabricated housing lends itself very well to additional bracing and custom-welded add-ons. Currie accompanies the F9 with domestic built inner and outer knuckles, brake rotor, caliper, and hub assembly inspired by Ford F350 and 450 trucks.
Overall, the F9 is lighter than its counterparts. Spare third members make life in the pits easier, and there are a ton of gear ratio options. The downfall is the lack of a high pinion option. In many JK Wranglers today, there is too much lift and pinion angles become an issue during the build process.
RockJock III 60
The RockJock III 60 is the first step for serious rockcrawlers. The third member housing was specifically designed for a high pinion set up with proper oiling.
It offers a large 3-inch tube and built in skid plate made of AR400 steel, the same stuff used for abused bulldozer buckets. Standard high pinion Dana 60 gear sets are used and feature an impressive 9.75-inch outside diameter ring gear.
The RockJock III 60 also uses the F350/450 inspired knuckle and brake assemblies to get the extra strength and durability when entering into the heavy crawling game. All of the RockJock 60s and 70s have a rotated diff cover, providing a round bottom, and are great for sliding off of rocks. Heavy throttle users and 40-inch plus tires need to keep moving up the scale.
RockJock VXR 60
If you are a hardcore crawler with lots of throttle use and massive tires, the RockJock VXR 60 is your entry point. Utilizing a huge 3.5-inch tube diameter and seriously beefed center casting while retaining Dana 60 carrier and ring and pinion options, the RockJock VXR 60 is a hybrid between the 60 and 70 differentials.
This housing offers the same AR400 skid plate as its little brother with the same high pinion. It adds the extra strength and durability of the RockJock 70 style casting, including a load bolt that helps to reduce or eliminate deflection in the ring gear under extreme duress. If you really like to abuse your vehicle, keep going.
The RockJock 70 is Currie Enterprises’ ultimate differential. It uses a huge 10.625-inch ring gear — large enough for a TJ and older Dana 30 ring gear to fully sit inside without touching each other. The casting is designed for the high clearance and high pinion set up. AR400 steel skid plate, load bolt, and extra webbing built in all make for a significantly higher weight and abuse rating. The only downfall to the RockJock 70 is the weight and price. Currently, it is the largest high-pinion differential available to the aftermarket.
Dynatrac was born out of necessity. Jim McGean founded the Southern California company by solving his own dilemma. When building his 1979 Ford F-250, Jim wanted a heavy-duty Dana 60 axle assembly to replace his broken factory Dana 44.
After finding the pickings from junkyards slim, and the front differential aftermarket non-existent, he decided to build his own. Dynatrac started in a garage as a part-time and one-man show, and now Dynatrac is one of the top shelf axle builders in the industry.
Let’s check out the pros and cons of each. The headlines:
- ProRock 44, a serious upgrade from stock JK Dana 30 and 44 with more ground clearance than the JK Dana 30.
- ProRock 44 Unlimited offers the same strength and durability that is standard on the ProRock 44, and then includes revised suspension brackets to increase the caster for better driveability on JK Wranglers with lifts over three inches.
- ProRock XD60 is the first of its kind, high-clearance housing, with impeccable strength and more ground clearance than a Dana 44.
Dynatrac’s ProRock 44 is a patented design that provides incredibly high clearance, even over a Dana 30. The center casting was designed to retain factory JK Dana 44 gear set and carrier to aid in ratio and locker choice. The entire axle housing is made in the USA and comes with Dynatrac HD balljoints installed from the factory. Dynatrac recommends no more than a 38-inch tire. Those with a need for bigger meats and/or tall lifts need to look below.
ProRock 44 Unlimited
The ProRock 44 Unlimited features all the same amazingness of the standard ProRock 44 except for the suspension brackets. Specifically designed for JKs with more than three inches of lift, the ProRock 44 Unlimited utilizes brackets designed to increase the caster for better alignment.
Better alignment means better driveability and control. While the alignment issues are sorted out with the ProRock 44 Unlimited, the tire size is still a limited factor. All of the ProRock 44 housings use a 3-inch diameter tube, and have wall thickness upgrades available, but those who enjoy heavy throttle and big rocks need to step it up once more.
The ProRock XD60 is designed for vehicles with lots of engine power, heavy tires, and drivers with an aggressive driving style. The center section is built from high-strength nodular iron, and the patented high clearance design provides more ground clearance than a JK Dana 44.
The ProRock XD60 uses a massive 10.1-inch ring gear and a larger carrier, increasing the overall strength 16 percent over the 9.75-inch ring gear Dana 60. Advanced engineering tools were used to increase rigidity, strength, and durability while dropping weight by 15 percent. The cons, while being lighter than a standard Dana 60, it is still heavier than a stock front JK axle assembly, and they aren’t cheap, but is the price paid to be nearly indestructible.
Dynatrac has spent years immersing its company and culture in the off-road lifestyle and will continue to innovate and provide excellent customer service for years to come. Its products are designed, manufactured, and assembled in the USA, and each goes through a gauntlet of inspections to ensure quality is the absolute best.
So … Which Product Should You Choose?
This story only scratches the surface of what product you should choose for your JK Wrangler. Both Currie and Dynatrac specialize in heavy-duty solutions to your needs and have knowledgeable associates ready to help you decide. Give them both a call to determine the best way to take your Jeep to the next level.