Beef Up Your 4×4 With The New Currie Enterpises RockJock 44 Axles

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If you don’t know much about Currie Enterprises, it pays to go back in time a bit. There are quite a few companies around today producing axle products for the off-road market, but Currie has been doing it for a long time and is a pioneer in the marketplace. Like so many others that are huge today, it got its start in a small garage.

Frank Currie began the business creating axle differentials and assembling rearends for electric carts, scissor lifts, material-handling equipment and other specialty vehicles. By the mid-’60s the Currie plant had grown to 5,000 square feet, and by the late ’70s, Frank’s sons Charlie, John and Ray were also part of the business. It was about that time they were all bitten by the off-road bug.

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Off Road Xtreme leads you through an insider’s tour of how Currie developed its new RockJock 44 JK axle housing.

Soon the Curries were not only building their own Jeeps and four-wheeling all over the American Southwest for fun, but also making aftermarket rearends for Jeeps, and rear-axle conversions for mini-trucks such as the Chevy Luv, Ford Courier and Toyota Hi-Lux. Not stopping there, the Curries became famous for their bulletproof 9-inch rearends (based on the Ford 9-inch axle) for street rods in the early ’80s.

Upgraded Dana 60 and GM 12-bolt rear ends became part of the Currie line-up in the mid ’80s. All kinds of goodies, such as axles, gear cases, suspension accessories, disc brake kits to go with its axle kits, and other Jeep performance products were becoming part of the Currie offerings by then as well.

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Off Road Xtreme was privy to ground-floor development of the new Currie 44, as engineer David Castillo explained how this test housing with an oil-flow viewing port was used to check fluid pressure and flow patterns on the pinion gear.

In 1998 the Currie off-road hobby that had motivated the expansion of the business became even more serious with the decision to compete in the first-ever rock-crawling competition. It was being held in Las Cruces, New Mexico, and the Curries wanted to see how they would do.

Their Jeep, called “Rocky Road” was outfitted with all the latest Jeep goodies the company offered, including a triangulated-link rear suspension design. Frank and John Currie finished second overall in the competition, and Jeff Waggoner took first place with his Currie-equipped CJ.

Since then, the Currie gang and the company have been involved in professional rock-crawling, off-road racing, and all kinds of other competitive automotive events.

This level of involvement meant that the company had much more than just a small stake in providing a high-quality product, and that’s where our story really revs up.

44s Everywhere

For decades, one of the staples of the Currie business was also the Dana 44. This axle is used in a multitude of vehicles. The Dana 44 was first manufactured in the 1940s by the Dana/Spicer Corporation and is still being manufactured today, in both a front and rear variant. The Dana 44 rear saw use in the 1940s and the Dana 44 front began production in the 1950s, and both are still in use today.

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This comparison of the new Currie 44 center (left) and the OEM 44 (right, exhibiting a typical failure) shows the obvious size and structure differences between the two.

More than a dozen automobile companies have built vehicles using Dana 44 axles. It can be found in everything from 1/2- to 3/4- and 1-ton trucks to SUVs, including Jeeps.

The Dana 44 front has been used on all kinds of vehicles including the Dodge Ramcharger; Ford F-100, F-150, F-250 pickup; IH (International Harvester) Scout Travelall and Pickup; and Jeep Jeepster Commando and Commando, Wagoneer, SJ, TJ and JK Rubicon.

The Dana 44 rear has been underneath the Jeep Wrangler Rubicon, Grand Cherokee SRT, Wrangler LJ Unlimited, XJ, MJ, CJ-7, both Grand Cherokees; IH Scout II and Travelall; Isuzu Rodeo; Honda Passport; and Nissan Titan, Frontier and Xterra.

(Left) All the new Currie 44 centers incorporate oil flow ports (seen on the inside the housing) for the flow-through oiling design that was first introduced on RockJock 60’s. (Right) This view of the Rubicon RockJock center reveals thicker flanges, the location for the Rubicon's electric locker power plug on top and the locker's indicator lamp connection on the side, as well as the huge ear and Johnny Joint.

Not only was there a huge market for Dana 44 replacement axles and upgraded 44s for Currie, considering how many trucks, SUVs and 4x4s there were running around with the axles under them; but there was the other side of the Currie business, and it is a big side of the business.

We’re talking about all those industrial carts, material-handling and specialty vehicles that got the company started. Currie had huge contracts for those vehicles and they all use Dana 44 axles.

The Trouble With 44s

You can easily see why the Curries would have felt a bit uneasy, to say the least, when the company’s source for Dana 44 center castings started to become a problem.

“We have one industrial client that we were still supplying with 44s using another vendor’s center until our new centers were in play. Outside of that, we were pretty much shut down on 44 production,” said Brian Shephard, Marketing Director, Currie Enterprises.

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A massive bombproof differential housing cast from 65-45-12 ductile iron is the centerpiece of the new and improved Dana 44 from Currie Enterprises.

The new heavy duty Currie 44 housings feature 3-inch x 0.375 wall tubes (top), as well as 3/16-inch-thick laser cut brackets (lower left) and new forged-steel heavy duty inner C-knuckles. No lightweight flimsy cover, the ductile iron Currie 44 cover plate includes a hex-head threaded fill plug that doubles as a dipstick (lower right) for easy checks on gear fluid level.

“We had phased out the current 44 product line, which used housing centers that we re-tubed and built new housings out of. We stopped buying them because all of the cores that were coming in were defective. We were getting so many bad units in a batch of cores that it was no longer cost effective.

“Essentially our 44 program was parked until the new product line was up and running. We engineered our own high- and low-pinion versions and worked with a local California foundry to create the 44 centers. That way we could design them, and maintain strict control over quality and materials. Now we are making our own new Currie 44 centers just the way we want them, and getting as many as we need, when we need them,” continued Shephard.

Currie 44 RockJock JK Axles

Three versions:

  • JK-44HPF1 High-Pinion JK Rubicon
  • JK-44HPF2 High-Pinion JK Non-Rubicon
  • JK-44LPR1 Low-Pinion JK Non-Rubicon

Rearend Assemblies:

  • Complete housing weight is 134 lbs.
  • Center material is 65-45-12 nodular iron
  • 5/16-inch min. thickness center casting
  • Side gussets are .920-inch thick
  • Tubes are 3.00 x 0.375-inch dom steel
  • Brackets are 3/16-inch laser-cut steel
  • Johnny Joints on upper mounts
  • Knuckles are forged steel
  • 30, 31, 33 or 35 spline packages

Even if the standard factory Dana 44 under your rig is in perfectly good shape, there are plenty of reasons to look into upgrading to the Currie 44. This becomes even more important if you are planning to do any serious off-roading. And it becomes nearly a necessity if you plan to boost your 4×4 with a lift kit and big rubber.

The factory Dana 44 has small gussets cast into the case and they were equipped with 2-1/2- or 2-3/4-inch tubes, the new Currie design 44 features massive gussets and 3-inch x 0.375 wall tubes,” explained Shephard.

“And the old 44s could have oiling problems because of the way they were built. We incorporated our flow-through oiling design, that was first introduced on our RockJock 60’s, so they would have better oiling on the pinions,” Shephard said.

Currie Differences

The new Currie high-pinion 44 features an extra large sump area to hold more oil than the standard high-pinion 44, and as the ring gear spins, it helps drive oil into a secondary port that is at the top of the axle center.

David Castillo, Engineer at Currie, who was involved in much of the critical design processes of the new Currie 44, told us, “The pinion bearings get lubrication from two different ports (instead of just one) that helps direct more oil to the cavity between the pinion bearings. It oils from the bottom and the top.

It also carries more oil, which aids in appropriate cooling and lubrication. Castillo recommends using 2-1/2 to 3 quarts of Currie 9+ 85-140 Gear Oil to fill the case properly.

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From left to right are C-knuckles from a stock Jeep axle, the Currie JK knuckle and for the sake of comparison, the Currie F-450 knuckle. The Currie JK knuckle is made of forged steel.

How does the all-new Currie 44 compare to the OEM 44? Shephard had some hard facts. “The new 44s are cast of heavy duty, ductile iron and while there is a difference in weight between the new Currie 44 center (58 pounds) and an OEM Jeep Rubicon Dana 44 center (34 pounds), as well as the complete axles housings–an OEM weighs 91 pounds and a complete Currie housing center with tubes, knuckle ends installed and all brackets installed, is 134 pounds–the new Currie units are much sturdier, so the extra weight is well worth it.”

The new 44 has massive gussets and much better oiling – David Castillo, Engineer, Currie Enterprises

It’s easy to the see the sturdiness of the Currie 44 center casting in the thickness of the wall size of the pumpkin and in the differences of the casting fins or bolsters (width/thickness) when you compare the new center casting to the old.

Shephard went on, “The OEM unit needs upper and lower gussets to reinforce it, and the upper gussets are 0.40-inch thick, the lower gussets are 0.250-inch thick. The new Currie housing is thicker and beefier all the way through, and has big side gussets that are 0.920-inch thick. That’s nearly one-inch!”

“As well, the construction of the Currie axle tubes are superior. Stock tubes are 2.500-inch by 0.250 wall dom steel; the Currie 44 tubes are 3.000-inch by 0.375 wall dom steel,” said Shephard.

The all-new Currie 44 cover plate is made from the same heavy duty ductile iron that the center section is cast from. This is no lightweight flimsy cover, and it includes a hex-head threaded fill plug that is also a dipstick, so that easy checks on gear fluid level are a simple operation.

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Prior to assembly, the center castings (top) are heated in an oven to expand the axle-tube holes, then a jig is inserted to keep them from being deformed in the press. The inner ends of the 3-inch axle tubes are coated with a lube and sealant (lower left) prior to pressing into the centers. A hydraulic press (lower right) is used to insert the axle tubes into the sides of the cast iron centers.

The “ear” on top of the Currie 44 fronts in which Currie’s own Johnny Joint is inserted (where the Jeep JK and TJ Wrangler upper control arms attach) is super beefy, too. These Johnny Joints are renowned for their sturdiness and easy articulation, and include a Zerk fitting for lubrication.

All of the spring perches, and other brackets for steering links and such, on the new Currie 44 are constructed of steel plate that is substantially thicker than that used on the original equipment axles.

Even the C-knuckles used on the ends of the 3-inch steel tubes that get inserted into each side of the new massive ductile iron Currie 44 centers are much thicker than the stock knuckles.

Decisions, Decisions

There are two types of 44s, a high-pinion and low-pinion design. Each have different applications. There are also some limitations to the Currie 44s.

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In succeeding work stations, the axle tubes are welded into place in the centers, and then the C-knuckles, shock mounts, spring perches and other brackets that are formed from the 3/16-inch sheet steel are welded on.

What is it’s engine power output? Current tire size as well as any plans for future tire changes and upgrades? Current suspension modifications and lift size, and plans for future suspension mods or lift changes?

Things like this need to be gone over with Currie sales representatives when you are in the process of selecting the new axle and gear sets for your vehicle.

Shephard talked about the major decision points between the high- and low-pinion centers, “It’s primarily for pinion angle concerns. Most rear applications (that a 44 would be applicable to) have a long driveshaft, so the angle is not terrible and the low-pinion can be used effectively.”

“In a front application, however, where the differential is very close to the transfer case and the driveshaft is probably short, lifting the vehicle causes the driveline angle to quickly be come extreme. Putting a high-pinion housing up front reduces this angle dramatically.”

Shephard went on to explain, “We can custom-build the Currie 44 to fit just about anything really, but I keep stressing to customers, ‘in applications that 44s are applicable to.’ In other words, they are only applicable in vehicles with up to 37-inch tires depending on application and driving style … but in the applications they are “ideal” for, typically up to 35s, we can do high- or low-pinion fronts and low-pinion rears.”

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One of the last stages for the finished axle housings is a place to cool and undergo inspection before moving on to final customer build-out or shipping.

“We will not build high-pinion 44 rears at all and if we think the customer has too much tire or too much power for a 44 differential, we’ll direct them to a bigger rear axle. However, we commonly build Jeep JK, TJ, LJ, XJ, MJ, YJ and CJ front and rear 44s, and Bronco front 44s.”

“We also have third version, or I should say a second version of the high-pinion Currie 44, and that’s designed as the Wrangler JK Rubicon front axle replacement, it’s designed especially for that model. The Rubicon crowd has had a terrible time with housing and inner C-knuckle failure. The new Currie housing features our heavy center with the 3-inch x 0.375 wall tubes, our 3/16-inch-thick laser cut brackets, and our own new forged-steel heavy duty inner C-knuckles.”

The Rubicon replacement unit accepts the factory axles, gears, electric locker, cover, yoke, steering and all outer knuckle, brake and hub components. All the customer has to do is buy the new housing and put his parts back in it/on it.” added Shephard.”

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This is a Currie RockJock JK high-pinion non-Rubicon axle, outfitted with Reid knuckles and Spyntech hubs, but customers can get it almost any way they want.

Multiple Choices

One of the best things about the new Currie 44 is that it can be purchased either as a center casting only or built out to a customer’s exacting needs for almost any vehicle, including dozens of configurations for any number of of Jeep variants, or ordered in the Wrangler JK Rubicon replacement configuration.

We can custom-build the Currie 44 to fit just about anything … 44s are applicable to. – Brian Shephard, Currie Marketing Director

For instance, Currie offers just about all of the parts and accessories you could ever want to build out your 44 axles. A quick scan of its extensive selection revealed the availability of Wilwood disc brake kits, ARB air lockers, Dana 44 Eaton E-Lockers, Yukon Zip Lockers, Detroit Lockers, TrueTrac’s, Currie Performance axle packages in 30, 31, 33 or 35 spline, and suspension bracket kits for a variety of vehicle models.

One of the many choices available is a RockJock low-pinion 44 front housing with TJ/XJ/YJ knuckles installed. This standard rotation 44 front end housing is an ideal replacement for stock Jeep front axle assemblies and recommended for use with tires up to 33-inches tall.

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Front view of a JK 44 Low Pinion rearend installed.

It can be custom-built to each customer’s specifications, the Jeep TJ/XJ/YJ Dana 30 style inner knuckles are installed, vehicle-specific suspension bracket installation is available, and the housing center carrier caps are included. It accepts standard Dana 44 carriers and the larger JK ring and pinion sets.

Then there’s the granddaddy. The RockJock 44 high-pinion JK Rubicon HD replacement housing. This is an all-new, heavy duty 44, 100-percent made by Currie, that uses all of the factory internals out of the customer’s stock JK Rubicon 44!

As is the case with all Currie high pinion 44’s they only accept the larger JK high-pinion 44 gears. These gears feature a larger ring gear than a standard 44 as well as a 29 spline Dana 60 size pinion gear.

Currie’s own all-new 3/16-inch laser cut, heavy duty JK suspension brackets are used for easy bolt-in installation on the RockJock 44 high-pinion replacement, and all holes are drilled and threaded for installation of the JK Rubicon’s electric locker, and Currie’s forged JK knuckles are installed.

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The Currie 44 Low Pinion Rearend installed under a JK Rubicon seen from the backside.

These empty replacement housings allow the customer to reuse all of the factory JK Rubicon front end components – right down to the hardware! The only other parts a customer would have to buy would be ball joints and inner axle seals that are not reusable out of the factory housing.

Currie Enterprises has come a long way in its decades of operation, but one thing has remained, and that was obvious to us as we toured the new facility during the production of this article. The entire company, and the Currie’s themselves, are dedicated to top-quality, tough performance parts for vehicles that live daily in a demanding environment and must survive.

From the drawing board to the shipping department, the message is “get it right.” One look at the new 44s, and it’s obvious Currie got this right.

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The Currie 44 High Pinion Rubicon axle ready to rock!

Article Sources

About the author

Stuart Bourdon

Growing up with a passion for cars, trucks and motorsports made it natural to seek a career in that direction. An education in photojournalism, a love of the outdoors and years of exploring the waters, deserts and mountains of Southern California led to working on boating, outdoor, RV and off-road vehicle enthusiast magazines. Off Road Xtreme is the newest adventure in his life-long love affair with vehicles of all types.
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