Photography: Trent Riddle and Joe Daniels
It seems that in the truck world, some ideas seem to come and go with regularity. One of them is locking hubs on 4×4 trucks. The very first 4×4 trucks didn’t have locking hubs, and then engineers decided to add that option. The advantage of this new innovation was that users could unlock the front axles to reduce drag, thus improving mileage, reducing parts wear and even improving steering ease.
Some truck buyers began to express a desire to have trucks without any hubs so that they didn’t need to get out in the snow and mud to lock the hubs. So, in the 1970s, the big three automakers again began offering light trucks without front locking hubs and fitted them with full-time 4×4 transfer cases. In response, the aftermarket, in the form of Doug Nash and later, Mile Marker, offered kits to fix the full-time transfer case, while Warn offered locking hubs for those applications. This gave owners back a few miles per gallon and reduced driveline wear.
The Uni-Bearing Dilemma
Since the mid-1980s, modern light trucks, 1 ton and lighter, have been increasingly produced with unit-bearing, non-locking hub front ends. While this is great for OEM production costs and keeps owners from having to get out and lock-in front hubs to use 4WD, there are disadvantages. The first drawback is reduced mileage from the added drag of turning the front axle assembly all the time. And the drag is increased if aftermarket traction aids, lockers or LSD units are added.
The second drawback is the inevitable failure of the expensive and unserviceable unit-bearings. The unit or uni-bearing on a modern 4×4 front end are designed to be easy to replace and last at least until the end of your warranty period, unless you own a Ford Super Duty. After that, look to replace them at a cost that is way more than the cost of a few old-style taper bearings and races.
Typically, unit-bearing assemblies can cost upwards of $500 each, and with the R&R on both front uni-bearings, you can spend in the neighborhood of $1,500 on a good day. To add insult to injury, if they fail on the road, the wheel assembly could come off. With an old-school spindle and taper bearing setup, the worst case scenario is that if a bearing fails, you can at least get to the side of the road.
Yukon Gear & Axle Free Spin System
By now, you are probably thinking that someone should make a kit to upgrade your truck to the old spindle, taper bearing and locking hub setup? Your wish has been granted––Yukon Gear & Axle has recently developed their Spin Free Kit for late model ¾ and 1-ton pickups.
The latest system from Yukon Gear is for 2000 and later Dodge pickups and for `94-99 Dodges, as well. The system is essentially a bolt-on install, although it helps if you have some familiarity with front axle assembly and disassembly. The kit comes complete with everything you need for the install, along with detailed instructions and a set of premium locking hubs, according to Yukon. Yukon Gear’s Free Spin system offers improved MPGs by not turning all the front axle components when the hubs are unlocked. More importantly, the kit does away with the expensive factory unit-bearing and replaces it with a tapered bearing setup and lock hub system. According to Yukon, this setup offers improved strength and reduced maintenance costs while reducing wear and tear on the front axle components, U-joints and even the transfer case chain.
Sled Pulling Solution
For those diesel enthusiasts who occasionally sled pull with their truck, the Free Spin setup allows you to run a front axle limited slip unit or locker without worry about tearing up the front end. The beauty of the system, when used with either a locker or limited slip, is that when you can put power to all four wheels, you’re making 100 percent use of all that diesel-generated torque and horsepower by spreading the power evenly to the ground. This translates into more-consistent pulls and more distance than with the stock front axle setup. And when it’s time to hit the road to go home, you simply unlock the hubs, and off you go.
Diesel World was one of the first to get its hands on a prototype Yukon Gear and Axle Free Spin Kit, which we installed in a 2007 Dodge 3500 4×4. Like many 1-ton trucks, the rig is used for towing; and once the warranty runs out, it will be modified to compete in street class sled pulling. The Free Spin Kit was a good first step toward that goal. We’ll install a front locker next.
Roger Nelson, of Hat Creek Engineering, in Blythe, California, did the install. Roger is considered the guru of the desert and made the install look easy. The install was fairly straightforward, thanks to a kit that has everything you need as well as detailed instructions. The following photos hit the highlights of a typical install. In testing, we picked up an additional 1 to 2 MPGs, as well––not bad for a bone stock 6.7L Cummins.
If you’re a heavy-duty Dodge truck owner looking for more MPGs out of that Cummins or you use your truck for either sled pulling or drag racing, Yukon Gear & Axle’s Free Spin kit is worth taking a look at. In the long run, it will save you both fuel consumption and repair costs for the stock unit-bearing.
Hot Creek Engineering
Yukon Gear & Axle
10411 Airport Road
Everett, WA 98204
The Competition-Only Alternative U-Joint
Free Spin kits from Yukon Gear & Axle don’t come with U-joints. They are designed to use your stock U-joint. Typically, if your truck has low miles and very little time in 4WD, the stock U-joints can be reused. If you want new U-joints, they can be ordered with the kits at an additional cost.
For standard street and trail use, a heavy-duty Spicer U-joint is the best option. However, if your truck is used for diesel drags or sled pulling, with little or no use on the street, a stronger competition U-joint is available. The Yukon Super Joint has a thicker cross shaft and larger journals for added strength. To increase the trunnion journals, the Super Joint uses a thin bronze bearing instead of roller bearings. This increases the strength but makes them unsuitable for street use, because the wear is accelerated without the roller bearings.