Sometimes the most pivotal components of a mechanism are hidden behind the scenes—out of sight. Without the magic behind the curtains, the system is rendered useless. In this case, we are talking about wheel bearings. Hidden within the confines of axle assemblies, front and rear, a couple of caged roller bearings at each corner of the Jeep are responsible for carrying the load of the vehicle and keeping the tires turning freely. These bearings are the unsung heroes of our Jeeps, and they need some love every now and again.
There are three main types of wheel bearing systems. A full-float system has two opposed tapered roller bearings that ride on a spindle to carry the vehicle load, independent from the axleshaft. Full-float bearing configurations are seen on the front axles of Jeeps from 1941-1986. In 1987, Chrysler updated their front wheel bearings to a newer-style unit bearing that is all one piece and bolts to the steering knuckle. Once a unit bearing is worn out, the entire assembly is simply replaced. The third wheel bearing system that all Jeeps from past to present with a Dana 44, AMC 20, or Dana 35 share is a semi-float rear axle design. Unlike the full-float hubs, a semi-float axle only has one tapered bearing on the outer section of the axleshaft, near the tire. The differential carrier bearing inside the axle pumpkin acts as the second bearing to support the system, and the axleshaft itself carries the load between the two bearings.
Almost all Jeep rear axles are semi-float axles and follow a similar process to replace the rear wheel bearings and seals. This particular axle is a 1973 Jeep CJ Dana 44. From left to right in this picture we see the bearing retainer collar, tapered roller bearing, outer wheel seal, drum brake backing plate, bearing retainer plate, and finally the axle flange/wheel mounting surface. There is also an inner oil seal that is seated inside of the housing. Some axle variations have bearing shims as well. Be observant as you disassemble to keep all components and shim stacks in order. Taking photos along the way helps get things back together in the right order.
Today we are in the shop rebuilding a 1973 Dana 44 rear axle that will make our broken-down Jeepster mobile again. It is not common for the rear wheel bearings themselves to go bad—as long as they have good lubrication. You are more likely to arrive at this job when you’re replacing or inspecting the rear brakes and notice that they’re caked with grease and muck from a bad axle seal, which can render your rear brakes useless. If you find yourself in this situation, here is a sneak peek at what is involved to get your Jeep back on the trail again.
For this project we skipped past all of the easy stuff like removing the brake shoes and hardware so we can focus on the bearing and seal replacement. This axle utilizes a flanged one-piece axleshaft. Earlier rear axles use a two-piece design that consists of an axleshaft with a tapered end and a hub that is fitted to the shaft with a woodruff key and matching taper. The outer roller bearing taper on a two-piece axle will face the opposite direction, but otherwise the process is the same.
After the brakes are removed, a wire brush is used to clean all the mud and rust off the mounting hardware before all six of the bearing retainer nuts are doused with some PB blaster. Give the penetrating lube about 20 minutes or so to soak in and do its job; it really makes a difference in how much effort is needed to loosen the nuts. These are special fine-threaded hardware and will be reused if they are not damaged.
Work smart, not hard. There will be a hole in the axleshaft flange to fit a socket through so you can remove the retaining nuts. Rotate the axleshaft around as needed to access all the hardware. Once they are all removed, use a rubber mallet to gently coax the axleshaft free. A slide hammer can also be used if you have one.
Once the axleshaft is removed, clamp it into a vise to keep it stable. You will need both of your hands to work on removing the old bearing retainer and bearing.
To remove the bearing retainer collar, use a drill to weaken it. Start with a small pilot hole and work your way up through several larger drill bits. Drill down about three-quarters of the way through the ring, not the whole way. It is very important that you do not drill into the axleshaft itself. Once your hole is drilled, use a chisel and hammer to fracture the collar. You can see the fracture crack in this photo. The collar will slide off the seat. Be careful to not damage the seal surface to the right of the collar.
Once the collar is moved out of the way, use a cut-off wheel to cut through the bearing cage. Again, extreme care needs to be taken to not cut into any place on the axleshaft itself.
Pry the bearing cage off the bearing and remove the rollers as well. They can be thrown in the trash. A cut-off wheel was used to score the inner bearing race as deep as possible without hitting the axleshaft. The bearing is pressed up to a shoulder on the shaft near the wheel mounting surface, so that is where the most caution needs to be taken. It was much easier to see what was happening and easier to control a small cut-off wheel on a die grinder than with a standard 4.5-inch angle grinder. It may also be a little easier to make the score line on a 45-degree angle instead of straight across like I did.
Once you feel the score line is deep enough, use a hammer and chisel again to fracture the bearing race. The bearing material is stronger and has less of an interference fit than the retaining collar does, so it will be tougher to get it to fracture. Take your time. If you need to grind a little more, that’s okay. Just don’t damage the axleshaft. Notice the missing wheel stud. Take the opportunity to replace any damaged wheel studs while the brake backing plate is out of the way.
Now that the hard part is done, we can move on to reassembly. After the bearing is removed, the brake backing plate and bearing retainer plate are cleaned and painted. A Timken SET10 bearing set was sourced from Amazon (ASIN: B000BZ93HK), which consists of the one-piece bearing and race, as well as the retaining collar. The one-piece bearing come pre-greased, which is really nice and avoids the need for a messy bearing packing step. The outer Spicer oil seal was also sourced on Amazon (ASIN: B00CXAMTLI).
A hydraulic press is needed to install the new bearing assembly. The bearing retainer plate is first put onto the axleshaft, followed by the brake backing plate. Zip ties are used to hold the plates up out of the way during the pressing operation. The outer oil seal gets some grease to lube the seal surface before it is slid into place, making sure that the inner spring is facing toward the bearing. Then the bearing is next. The Timken SET10 instructions inform you to place the groove on the race toward the axleshaft flange. Finally, the retaining collar goes on last. The entire assembly is placed into the press and slowly pressed down until the bearing is seated against the shoulder of the axleshaft.
The old inner axle seal was removed and the bearing cavity was cleaned before the new inner axle seal was installed using a seal driver or large socket. A new Timken oil seal was sourced on Amazon as well (ASIN: B000BZABDA). Lube the seal with some grease once it is in place.
Next, we installed the axleshaft with the new seal and bearing assembly. You will need to use a mallet to tap the shaft and bearing into place.
Once the axleshaft is seated, tighten the bearing retainer hardware and you are done. Your axle now has brand-new bearings and seals, and it is ready for action.