Warn Alloy Front Shafts and Ox Joints Install

Big Axle Beef in a Small Axle

story and photos by Jim Allen

When you combine a diesel that cranks out 450 pound-feet, low gears, sticky Pro Comp tires and rocks, you need a strong drivetrain. The front-axle shafts and u-joints have always been the weakest axle link on many rigs with half-ton axles. In the case of the Bum-V, which was built on a K5 chassis, tire size has always been moderate, no more than 37 inches. That’s pushing the 10-bolt OE axle hard, but with some Warn shafts, Ox u-joints, and other mods, it’s now up to the task.

Weak front axles. It’s the age-old four-wheeling problem, a swap to a physically larger axle the only truly effective cure. It’s a good solution — or not — depending on the ease of the swap and the cost. There also are issues of the extra weight and loss of ground clearance that come with a bigger axle. What’s most irritating is that many people just need extra beef, not a major swap.

Today, there are swapping alternatives for many axles. Here’s one: replace the weak OE 1040 carbon-steel shafts with Warn’s 4340 chrome-moly shafts (inner and outer) and the weak u-joints with what may be the strongest u-joint on the market — the Ox.

What do you gain? On an axle in the Dana 44/GM 10-bolt strength area, 162 percent is gained over a standard-necked inner shaft (almost 100 percent over a non-necked 1040 shaft), almost 100 percent over a standard outer shaft, and at least 300 percent over the best standard u-joint (according to the manufacturer). Interestingly, that puts an axle-shaft assembly strength some 50 percent stronger than a stock Dana 60 shaft assembly.

As an assembly, the Warn axle/Ox Joint combo is more than two-times stronger than the Dana 44 shaft above. Beyond the necked section, note how much thicker the Warn shafts are in profile than the Danas. It always comes down to the thinnest part of the shaft assembly being the weakest. In the case of the Dana shaft, that’s in two places, the necked section or the minor spline diameter of the outer shaft. The smallest part of the Warn shaft is the minor spline diameter of the outer shaft, but, because of the improved material, it’s more than two times stronger than the OE piece at the same spot.

Front Axle Beefing — a Matter of Balance

Before you get all starry-eyed about having a Dana 60 in a Dana 44 package, there are some caveats. When combining strong axle shafts and u-joints with the remaining ordinary parts, bear in mind that torque is going to find the next weakest part. Usually, that’s the locking hub — a good thing, as it’s easy to replace.

There are better and worse hubs. Industry-wide, the better premium hubs will handle up to about 5,400 pound-feet. The average OE hub, or standard aftermarket, will take about 3,300. That lower number is okay in the stock realm, considering the weakest link on a standard D44/10-bolt axle is only good for about 2,400 pound-feet. It’s not so hot when the weakest part of an axle-shaft assembly can handle over 5,000 pound-feet.

If wheel hubs are the two-piece style (CJ-era Jeeps and some older trucks), an upgrade to the internally splined type will add beef, whether it’s a compatible OE-style or Warn’s super-strength aftermarket units. All this will raise the torque limits of the weakest links and give a much stronger unit overall.

What about the other parts? Most ring and pinions are adequate when set up properly, if gear ratios are not too low (the pinion is smaller the lower you go). Stock open carriers in the D44/10-bolt range are fairly weak. A swap to an aftermarket locker or limited-slip often comes with a new carrier, and it’s almost always stronger than the original. In a few cases, there may be stronger open carriers to choose from.

Bottom line, remove the weak links on the half-ton-style axles to run 35-37-inch tires with relative impunity on heavier rigs and even larger meats on light rigs. In most cases, a set of Warn axles combined with Ox Joints is cheaper than a Dana 60 swap and easier to install.

Yield Strength versus Tensile Strength

Yield Strength is the amount of torque an axle can absorb before it permanently deforms. It may not actually break, but it loses most of its strength. Yield strength will be a lower number than Tensile Strength, but it’s a more generally useful value because the material is still toast.

Tensile Strength is the point at which the material actually fractures. This will be a higher value than Yield Strength. See the “Steel Grades” sidebar.

Warn Shafts

The Warn shafts are made of SAE 4340 chrome-moly steel alloy, a material that’s nearly 100 percent stronger than the standard SAE 1040 carbon steel used on most OE front shafts. The inner shafts are not necked down like most OE shafts, and the yokes are beefier. Combined with the improved steel, that adds up to a unit that’s vastly stronger than stock. In fact, if you break a standard u-joint, most times the Warn yokes will survive — unlike a standard axle. On top of that, Warn offers a lifetime warranty when used with a standard Spicer u-joint. We have to be fair to Warn and stress the point that the warranty doesn’t apply if you use any of the so-called “super” u-joints on the market, including the Ox. In most cases, these u-joints are actually stronger than the axles.

The Ox Joint

The Ox Joint is a uniquely designed u-joint that carries the drive torque inside the axle yokes and, according to the designer, this tends to enhance axle strength. Like most super joints, it uses bushings instead of needle bearings. This reduces life when measured in hours of operation, so it’s not designed for a lot of highway use or full-time four-wheel-drive rigs. What it loses in hours, however, it gains in brute strength. The manufacturer has destructively tested it to 22,000 pound-feet. For perspective, the latest Spicer 760 series joint tests at 5,400 pound-feet in the same type of destructive test. The previous Spicer 297 series joint averaged about 4,500 pound-feet in the same test. Because of its strength, the Ox must be used only with 4340 alloy axles. Otherwise, you’ll be busting axles right and left. The Ox will fit most 4340 front axles set up for full-circle clips, including Warn (except for some of the earliest production pieces from about 1997), Genuine Gear, Yukon, and Superior. They may have problems fitting some Moser front shafts.

Steel Grades

There are many steel grades, but only a few are used in axle-shaft construction. The first two numbers indicate the steel group. The second shows the carbon content in hundredths of a percent. Bear in mind that actual yield and tensile strength varies among manufacturers according to the exact steel recipe used. The fine details are often proprietary.

SAE 1040: Carbon Steel Group. Commonly used by the OE, carbon steel can be made strong with proper heat treatment and this makes for a cost-effective material. Average yield strength, 110,000 psi. Average tensile strength, 125,000 psi.

SAE 1050: Carbon Steel Group. Used by the OE in some applications and used by many aftermarket builders of replacement axles. The extra carbon makes it respond better to heat treatment. It’s more expensive to produce, but it’s still cost effective based on its strength. Average yield strength, 140,000 psi. Average tensile strength, 160,000 psi.

SAE 1541H: Carbon Steel Group. Used by many aftermarket builders of high performance parts. The 15-series carbon steels have more manganese than the 10-series steels. This makes it respond even better to heat treatment. The “H” indicates a dash of extra silicon, which increases hardness. 1541H is more expensive to produce than other carbon steels, but it’s still cost effective based on its strength. Average yield strength, 160,000 psi. Average tensile strength, 180,000 psi.

SAE 4340: Nickel Chromium Molybdenum Steel. Used by the aftermarket for high-performance axles. There are many variations in this general classification, including 300M (a.k.a. 4340M) and Hy-Tuf. Average yield strength, 215,000 psi. Average tensile strength, 230,000 psi.

Installation

The actual installation is similar to changing any front-axle joint. The main differences are with the u-joint itself. For that reason, we’ll focus on the unique parts and streamline the rest. The service manual can provide you with the basic R&R info.

Wrench Rating: Ratings Explanation		1. The necked-down portion of the D44/GM 10-bolt inner shaft is a major weak link. It measures 1.10 inches and will yield at approximately 2,400 pound-feet. This makes it about equal with the outer stub axle in strength. There are some non-necked replacement shafts out there (usually blanks cut to fit) of 1040, and these are much stronger, yielding at about 3,100 pound-feet. Incidentally, this necked area is the same on GM 10-bolt 28-spline front axles, rendering the Dana 44’s 30-spline advantage essentially moot, unless it has non-necked shafts. A 28-spline 10-bolt non-necked shaft would be rated at around 2,700 pound-feet.
2. The Ox u-joint uses a multi-piece design. The center body is made of 8620 steel alloy. The Ox has pins that insert through the axle yoke ear into the body, retained inside a cavity in the body by a pair of 4340 alloy retainers. The pins also are 8620, but they get a different heat treatment than the body. The pins use an o-ring seal to keep water out.		3. Remove locking hub, bearing nuts, and finally the wheel hub/brake rotor. Now is a good time to repack the wheel bearings and replace the hub seals.
4. Remove dust shield and spindle. The nuts are often self-locking. On installation, either replace the nuts or use high-strength (red) thread locker to make sure the old ones don’t work loose.		5. Start with the new inner shaft, securing it in a vice while protecting the shaft from damage with rags. Slide the Ox body between the yokes. If installing the Ox on used axles, remove rust from the inner-yoke surfaces with a file and smooth out the pin bores with Emery cloth or a file. It should be a snug fit, not super tight. If it’s too tight, the ears may be tweaked on the axle or you might have left a small burr that needs to be filed away.
6. Make sure o-rings are installed on the pins, pushed down into the grooves, and lightly lubricated.		7 a & b. Press the pins though the yoke ears into the center body. This can be done with a vise or a hammer (as shown) or with a hydraulic or arbor press. Light lubrication of the pins is helpful.
6. Make sure o-rings are installed on the pins, pushed down into the grooves, and lightly lubricated.		7 a & b. Press the pins though the yoke ears into the center body. This can be done with a vise or a hammer (as shown) or with a hydraulic or arbor press. Light lubrication of the pins is helpful.
8. Slip the outer yoke over the body, lightly tapping the pins in, then pressing them as in the previous step.		9 a, b & c. It’s difficult to get pins installed exactly to the right depth to install the pin retainer. It’s easy to drive them farther in with a hammer, but the special tool provided can be used to pull them out slightly. Remove the Allen screw from the outer end of the pin and screw in the bolt from the tool. The deeper the bolt is screwed in, the more it will pull the pin out.
10. Once pins are in the correct position, install one of the retainers. As you can see, there is just enough room to get the retainer installed with the joint fully articulated.		11 a & b. Make sure the retainer is fully seated. Put Locktite (provided) on the threads of the cap and install the cap using an Allen wrench. The cap doesn’t need to be super tight. Repeat this and the previous step on the other side.
13 a & b. On reinstalling the Ox, assembly might not fit though the hole in the knuckle. If that happens, use a die grinder to notch the hole in four areas so the unit will fit though.		14. The axle reassembles normally from this point. It’s a good idea to upgrade to premium hubs here or solid drive flanges for maximum strength.

Sept 2005

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