Many folks may wonder why anyone would want to rebuild the Jeep/AMC 20 two-piece rear axle. It's a good question, as this axle is often considered a weak link in most Jeeps that sport it. The most common complaint is the splined two-piece design, which is notorious for spinning under extreme off-road use. If you're going to the trouble to rebuild, some would ask, "Why not install heavy-duty one-piece units?"
The fact is not everyone has the financial means to do this sensible swap. The 20 can be rebuilt with new service components for a fraction of the cost of installing one-piece axles. Furthermore, not everyone will put their Jeeps through the kind of rigors that have been known to claim the 20 in the past. We plan to upgrade to one-piece axles somewhere down the road, but for now the prudent course is to rebuild this 20 to stock specs.
Rebuild components for the Jeep/AMC 20 are not difficult to come by, if you find a quality source. For that task we went to Light Line of Louisiana for axle internals. Light Line is fully stocked with new and used parts for Jeep CJs, Wranglers, and J-trucks, in addition to carrying dealer and aftermarket parts for practically any application. Earlier we ordered the outer axle seals and some components not necessarily included in an inner axle rebuild, along with new brake components from Savanna Jones.
If you would like to upgrade to one-piece axles, the following how-to can also be employed for a successful one-piece installation.
After disassembling the brake...
After disassembling the brake system, remove the dust cover from the axle hub. On a vehicle that has not been serviced in a while, this may require some serious persuasion. Next, pull the cotter pin from the castellated axle nut, then remove the nut.
Remove the four bolts that...
Remove the four bolts that secure the backing plate to the axle housing. Pull the axle/backing plate/drive flange assembly from the axle housing.
A special puller that hooks...
A special puller that hooks on the wheel studs is needed to remove the hub from the axle. Never use a puller that pulls on the edges, as it will usually bend the hub. Once the hub is off, remove the protector backing plate, the shims, and the seals. Be careful not to lose the small keyway that indexes the hub to the axle.
A press is used to remove...
A press is used to remove the old bearing, as well as to install the new one. Make sure the taper of the rollers faces the correct direction.
To tear down the differential,...
To tear down the differential, pull the axle cover, and remove the two carrier bearing caps. These must go on the same way they came off, so don't mix them up or turn them around. Note the orientation of the axle housing during disassembly to help make sure the caps are properly reinstalled.
Shims are located on the outside...
Shims are located on the outside of the carrier bearing caps and usually come out with the carrier. Carefully pull the unit out of the housing, and keep the shims separated according to the side on which they go.
Remove the pinion nut and...
Remove the pinion nut and driveshaft flange from the pinion. Knock the pinion out of the housing by tapping on the end with a brass hammer. Remove the pinion seal, followed by the pinion bearing.
Use a hammer and drift to...
Use a hammer and drift to drive out the inner pinion race, then remove the pinion race and shim(s) from the inside of the housing. Working from inside the housing, drive out the outer pinion race.
After removing the outer axle...
After removing the outer axle seals, thoroughly clean the housing before reassembly. A scrub brush lashed to a broomstick allows you to clean out the axle tubes quite nicely.
Use a press to remove the...
Use a press to remove the inner pinion bearing and the two bearings located on either end of the carrier.
Place the pinion shim onto...
Place the pinion shim onto the inner race shoulder, and install the new inner pinion race so that it rests on its shoulder. The outer pinion race is installed the same way.
Using a micrometer, measure...
Using a micrometer, measure the thickness of the pinion and carrier shims. Considering that the original ring-gear-and-pinion was reused, the original shim are reinstalled as a starting point.
A press is also necessary...
A press is also necessary to install the bearings without damaging them or yourself. Care must be taken not to also damage the bearing cage during installation. A thin-walled steel tube was used here to install the bearing.
The pinion is lowered into...
The pinion is lowered into the housing and rests on the race. Lubricate the bearings with motor oil before installing.
Slide the new pinion bearing...
Slide the new pinion bearing preload shim (crush sleeve) over the pinion shaft. Next, install the outer pinion bearing. Don't forget to lightly lubricate the bearing rollers and race to prevent damage during setup. The bearing may need to be lightly tapped into place.
Use a brass hammer or a seal...
Use a brass hammer or a seal installer to properly seat the pinion seal. Next, install the pinion flange and nut, and tighten the pinion nut until all slack is taken out of the yoke and the bearings are fully seated against their races.
The ring-gear carrier with...
The ring-gear carrier with new bearings and races is lowered into the case, then the original carrier bearing preload shims are reinstalled in their respective places. The bearing caps are reinstalled in the same orientation as they were removed, and the bearing cap bolts are torqued to 87 ft-lb.
Using a dial indicator securely...
Using a dial indicator securely attached to the differential case, the ring-gear backlash is checked. Set the indicator at a 90-degree angle to the face of the ring-gear-tooth contact surface. The backlash should be within the factory recommended 0.005 to 0.009 inch.
After coating the ring gear...
After coating the ring gear in multiple places with gear-marking lube, the ring-gear-to-pinion-gear contact pattern can be observed. A contact pattern in the center of the ring-gear-tooth face is desired. The pattern can be adjusted with bearing shims to move the ring gear from side to side, and to adjust pinion depth.
The final pinion bearing preload...
The final pinion bearing preload is set by tightening the nut until the pinion can be turned with a force of 17 to 18 in-lb. Install the cover with a new gasket.
After installing the inner...
After installing the inner axle seals, pack the axle bearings with grease. Smash the grease into the inner side of the bearing until it comes out the other side. Slide the axle into the housing, and install the bearing race until it seats into the housing.
Axle shaft endplay is adjusted...
Axle shaft endplay is adjusted by slims placed between the housing end and the backing plate. Install the passenger-side axle, the backing plate, the outer seal, and the protector. The driver-side axle endplay is adjusted to 0.004 to 0.008 by adding or subtracting shims. Then install the backing plate to check. Once adjusted properly, install the seal and the protector as well.
Reinstall the axle key, and...
Reinstall the axle key, and slide the hub onto the axle.
The rear wheel hub nut is...
The rear wheel hub nut is seated on the axle splines and spun with an impact gun. Final torque will be set when the full weight of the vehicle is resting on the tires and set to a minimum of 250 ft-lb.