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4x4 Wheel Hub Upgrade - Diesel Tech

How To Upgrade Your 4x4 Wheel Hubs

Gary Wescott
Mar 20, 2007
Photographers: Gary Wescott
Photo 2/11   |   The Dynatrac Free-Spin Hub Conversion Kit for the Ford 4x4 Super Duty and Dodge Ram comes complete with all bearings, seals, and replacement spindles, hubs, and stub axles.
The unit bearing was a great engineering breakthrough. Imagine the time it once took to set up and properly adjust the front hub bearings on big Ford and Dodge 4x4 trucks on the assembly line. A unit bearing is all neatly packaged and sealed-no mess, no greasy fingers. Plop it in, tighten a few bolts, and send the truck down the road. However, as with all new things, there were bugs.
No Service
Unlike older front hubs/bearings, these sealed units cannot be serviced, and they have been known to fail without warning. When they die, the damage can be extensive. The replacement bearings alone can run about $400, plus new studs, nuts, an external O-ring seal, and labor. If it's not caught in time, the rotor, spindle, calipers, brake pads, and the stub axleshaft-basically everything in front of the galvanized brake dust plate-are history. All this can happen in just half a mile when you are driving 65 mph!
Photo 3/11   |   The inner and outer bearings in the OEM hub are stacked right together, which decreases their mechanical ability to absorb the leverage. The Dynatrac design is much stronger, and the bearing cage is steel.
Better Bearings
Bearing maker Timken told us its bearings are engineered to have an expected life of 150,000-200,000 miles. That's quite a spread! In fact, the front hub bearings in our own Ford F-550 Super Duty failed at something under 10,000 miles. With heavy loads and/or bigger tires, failure rates increase. However, many people who appear to be using their Super Dutys or Dodge Rams under normal conditions (stock tires and light-duty use), have experienced failures within the first 50,000 miles. Unit bearings are often considered to be a "normal wear" item and, therefore, are not covered by warranty at any mileage level. Some dealers may approve this type of work under warranty on a case-by-case basis, but one-time repairs at a dealership can easily exceed $1,500.
Photo 4/11   |   The pre-assembled rotor, dual wheel adapter spacer, and the new hub combine to make a rather heavy part to lift and slide over the spindle later, especially on F-550 and F-450 models. Individual components can be fitted one at a time to the steering knuckle.
Warning Signs
There are some signs to look for that may indicate your wheel bearings are close to failure. If the ABS light comes on and stays on, it may mean the tone ring located between the two sealed wheel bearings is wobbling. If this happens, immediate inspection is a good idea. Excessive heat and/or uneven brake pad wear is another sign of problems. The old jack-it-up-and-wiggle-the-wheel method can also tell you if something is amiss. Also, check if overheated grease is seeping out from the seal. You can also spin the wheel and listen for a grating noise. But you have to do something before the bearing fails-none of these tricks is much help when you're stranded on the side of the road with a truck that won't move.
The Fix
Fortunately, now there is a solution. Dynatrac has designed a "fixed spindle" unit that is far superior to the factory "live spindle." This is similar to the serviceable hub and bearing assemblies we have known since the early 1980s. The new spindle is forged from chromoly steel, and a cast nodular wheel hub replaces the OEM unit. The kit also uses Warn Premium manual locking hubs to engage or disengage four-wheel drive (a definite upgrade for Dodge drivers, who lost manual hubs after the '93 model year).
Photo 5/11   |   The new spindle is forged from chromoly steel. This is a traditional fixed spindle. The new hub rotates around it.
Dynatrac engineers also upgraded the OEM 1.31-inch, 30-spline outer stub axle to a stronger 1.50-inch, 35-spline unit. The conversion uses all stock components-rotor, caliper, and brake pads-and is fully compatible with the stock ABS sensor. The Timken bearings, races, and seals are the same as those used on '86-'97 F-350 4x4 trucks and are also common to many Dodge and GM 4x4 trucks. The parts can be purchased at any parts house for about $65 and can be inspected, repacked, and adjusted as part of normal service.
After experiencing bearing failures on two occasions on our '99 F-550, we took the opportunity to visit the Dynatrac facilities for a close-up look at the new conversion kit and the installation process. The owner of Dynatrac, Jim McGean, explained that the sealed OEM unit bearing had several problems. First, the two bearings are stacked right together, which decreases their mechanical ability to absorb the leverage exerted by the wheel. On dualies, this is compounded by the large dual rear-wheel spacer/adapter installed on the front axle, further increasing the leveraged force on the bearings. While the bearing may come from the factory properly greased and torqued, the sealed units cannot be inspected, adjusted, or serviced, so when the seal begins to leak or any contamination gets in, the bearings can overheat, causing more grease to escape. All of this is further aggravated by the fact that the bearing cage in the OEM unit is plastic, not steel. Once extreme temperatures are reached, the cage melts and total failure is rapid and complete.
Photo 6/11   |   The original steering knuckle and all steering components are retained. When the kit is correctly installed, there is no effect on wheel alignment.
How To Upgrade
The installation of the Dynatrac conversion kit is straightforward and can be done at home by anyone who knows the basics of repacking wheel bearings. After setting the brake calipers aside, the OEM hubs, brake rotors, and axles were removed; the factory steering knuckle remains in place. All parts were thoroughly cleaned to prevent any contamination. The Dynatrac technician pre-assembled the rotors, dual wheel adapter spacers, and the new hubs on the bench. This makes a rather heavy part to lift and slide over the spindle later. Individual components can be fitted one at a time to the steering knuckle. The dual rear-wheel adapters and brake rotors on the front axles of F-550 and F-450 trucks are considerably heavier than those on F-250 and F-350 models.
Since the OEM stub axle is not reused, we took the opportunity to replace the U-joints on the new 35-spline outer shafts with high-quality Spicer joints. The axles were then slipped back into the axlehousing, aligning the splines with the differential gears. Machined needle bearing housings were mounted on the back of the new spindles, and the larger needle bearings were installed with their seals. After reinstalling the dust shields, the spindles were aligned with the holes in the steering knuckles and secured, and the ABS sensors were fitted to the mounting blocks on each spindle.
Photo 7/11   |   The replacement needle bearings are significantly larger than those in the factory unit hub.
With the new bearing races installed in the wheel hubs, the bearings were packed with grease. We did it the old-fashioned way-by hand. Make sure you grease the bearings; they come with a protective coating, but they are not greased. The instructions note the importance of making sure you have the correct wheel studs because there are two different types: fine and coarse threads. Dynatrac can supply either one.
After the inner bearings are packed and installed, the complete hub/rotor/dual wheel adapter assemblies can be slid over the spindles, using care not to damage the inner hub seals. Now the outer bearings can be installed with their spanner nuts and tightened to the correct torque. The new Warn locking hubs slide in easily and are held in place by large internal snap rings.
Photo 8/11   |   The new Timken bearings were packed with grease the old-fashioned way-by hand.
Finally, the stock calipers were reinstalled. Spacers are provided to ensure proper clearance between the pads and the brake rotors. On our F-550, the small tabs on the dust shields that cover the ABS wires needed slight trimming so they would not rub on anything. When the kit is correctly installed, there is no effect on wheel alignment. For Super Duty trucks with big suspension lifts, the original Dynatrac Super Duty Combo Kit is still available. This requires changing steering knuckles and the track bar, and takes considerably more time. The conversion we installed required no welding, drilling, or grinding.
The complete kit comes with detailed step-by-step instructions. The only special tools required are: a six-point spanner socket (OTC #7090-A) or a four-point spanner socket (OTC #7158), depending on which style spanner nuts your hub needs; a torque wrench that will go to 140 pounds; and a race driver like the one made by Snap-On (#PPC14LA). Note: Tools needed for the Dodge kit may be slightly different.
The Dynatrac Free-Spin Hub Conversion kit for Ford fits all Super Duty 4X4 trucks from '99-'04. A kit for the '05 and '06 Super Duty (which, despite a larger bearing, still suffers from the same problem), is being developed. The kit costs $1,695.
A Free-Spin Hub Conversion kit for the '94-'99 and '00-'05 Dodge heavy-duty trucks is available, with the added benefit of giving Dodge truck owners manual locking hubs. These will help increase fuel economy and reduce wear and tear. In other words, the axleshafts, gears, and driveshafts won't be constantly turning with the hubs unlocked. The kit costs $1,795. Both are available directly from Dynatrac or any of their dealers nationwide.


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