Rear axle bearing replacement

These are basically my personal notes to myself, expanded into a how-to. I have no pictures for this page; I only wrote it up after someone asked for tips on the AMC forum, the week after I'd just done the job. If you see an error in my method please let me know.

Tools you will need, not usually in casual toolboxes:

Disassembly

With the car on the ground, pop the rear hubcaps, pull the cotter pin from the axle end. Put the car in reverse (or Park), put the parking brake on, hard. Assemble the 1-5/16" socket on the breaker bar and extention, stick it on the axle nut. You must support the extention with a jackstand or something such that it is concentric with the axle -- if you do not you will round off the nut.

Put the breaker bar horizontal and stand and/or jump on it. It takes a lot of force to crack that nut loose! Remove the nut.

Now jack up the car, remove wheel, brake drum (might have to back off the adjuster as per TSM), all the brake parts, etc. Wire brush the heavy crud off, especially around the axle tube bolts and the wheel cylinder (avoid crud in the brake line). Before removing the hydraulic brake from the wheel cylinder, prepare a 2" piece of 1/4" fuel line, plug one end tight with a junk bolt or screw. Use the flare nut wrench square on the flare nut, take off the brake line. When you get the line off the wheel cylinder, jam the plugged hose chunk onto the flared tubing to keep the mess down.

The parking brake cable snaps into its hole in the backing plate, retained by little fingers that pop out. To extract it, get a small worm drive hose clamp, 1/2", fuel line size. Open it and place it around the finger area of the brake cable, inside the backing plate, and tighten it such that the fingers are pressed in. Now just drive the cable out with a punch and hammer. Doesn't take much force, it'll slide right through the hose clamp.

A pair of 9/16" combo wrenches gets the four bolts holding the backing plate to the axle tube off. Because the hub is still pressed onto the axle, everything comes out as a unit -- axle, outer seal and shims, backing plate, hub. In theory the axle and junk just pull out of the axle tube, but it will be nicely stuck. The TSM shows a nice puller for this but requires the hub off (and few of us own AMC service tools). Put a brake drum on, backwards, with three nuts, 2 - 3 turns only, and use it as a slide hammer. You can also kick -- with your foot! -- the backing plate -- this will lever the stack of parts off the axle tube. Using only your foot you'll do no damage. It will take some wrastling to extract it all.

The axle assemblies go to the shop for disassembly and bearing replacement -- I don't own a press. It is critical to MARK ALL THE CRITICAL MATING PARTS NOW! before you take them to the shop. I have a letters stamp set, but use two file or hacksaw notches for left, and three for right, or something. (Don't use one notch, too hard to ID later.) Paint won't work. Mark the hub and axle end now since they must remain a pair and the shop will separate them.

Have your shop press off the hub and bearing, and press on new bearings. Keep the outer bearing race at home. Note that the race goes on from the outer end of the axle after it is installed in the car -- make sure the shop doesn't put them on backwards. Do not let the shop press the hubs back on, you'll do that at home. I also have the brake backing plates hot tanked and media blasted. Don't do the hubs or axles, not need, plus it will hurt mating and journal surfaces.

The inner seals must be replaced. Pull the old ones out now. I make a puller from a rectangular scrap of steel about 3" long, drilled and tapped in the center; a piece of threaded rod and a plate over the axle tube end make a puller.

Before reassembly

I pack the bearings, now on the axles, first thing, and wrap them with waxed paper to keep them clean and ready. The brake backing plates, I weld up the nasty wear grooves, where the shoes contact it, and grind them flat again. They'll work better and last longer. I paint the with Chassis Black. At this point I prep everything; pre-lube new parts, clean up existing parts thoroughly, including axle tube ends inside and out, scrape shims clean and flat, etc. Assembly goes faster and cleaner.

Soak the new inner seals in light oil -- I use Marvel Mystery Oil -- overnight. Even new parts likely sat on the shelf for years, they need to be soft and oiled or they will burn up if run dry.

Assembly

First thing to do is install new inner seals. I wipe them off, and get the axle tube and seal metal oil-free with brake cleaner. These are critical, and easy to deform. Do not drive them in with a punch, they will be ruined. I use a piece of pipe or other object just small enough to fit in the axle tube, square on the end; then drive the seal in with taps around the edge of the pipe until seated. The TSM says to coat the edge with sealer; I find this gets lost during installation, so I install them dry then put a bead of Right Stuff (by Permatex) around the perimeter and smooth it with my finger. This stuff didn't exist back then!

The axles insert next. Do not let it scrape up the inner seal! Support it with your "other" hand and insert slowly. At some point it will clunk; lift it concentric with the tube and insert it into the splined socket. BEFORE YOU DO THAT! apply light oil to the inner seal's journal surface, just behind the bearing. Failure to do so will run dry metal on the seal and it will burn up fast. Once the axle is seated, pack the space between the bearing and tube with grease, then press in the outer race. The axle is now in it's more-or-less final spot.

Install, in order, shims (driver side only), outer seal, backing plate, putting gasket sealer between all parts. Bolt it back up (replace lock washers). Torque spec somewhere in the TSM.

Once both axles are in, you should check end play, as per the TSM. The last three times I've done this job, carefully cleaned the shims and reinstalled, it was within spec. Bearings these days, made all over the planet, probably worth checking, but it's likely it will be "OK" if you don't measure it. But I hate to do jobs over again... I check.

All the brake junk goes back on normally. Install brakes on both wheels now; the reason for this will be clear later. Easiest to bleed the brakes with no wheels attached!

Hub reassembly

When it's time to reinstall the hubs, get everything degreased, wire brush the old serrations in the axle. Brake parts all installed. I'm paranoid about spinning an axle in the hub... so I put medium Loctite on the serrations before assembly. Note that the stuff cures in 10 minutes so if you do this, get everything ready to go all lined up so you can do this in one step.

Before you assemble, file and sand the bottom of the nut and the stamped side of the thrush washer flat and smooth. (All washers have a smooth, stamped side and a rougher bottom side). This is will affect reinstallation torque.

Place a brake drum over the brake shoes on the side you are NOT doing first. Though there's no hub there yet, this will let you use the parking brake, which you'll need to keep the axles from rotating as you retorque the hubs on.

Hub goes on the axle -- you marked axles and hubs left and right, correct?! -- then lubricate (preferably engine assembly lube or ARP fastener lube) the thrush washer, nut face and threads. Wrench 'em on as best you can with the car still in the air.

Install a wheel and tire, three lug nuts is enough, drop that wheel on the ground, put the transmission in reverse/Park, put the parking brake on hard (this is why you want to assemble the brakes first, and put a drum over the other side). Now set up the 1-5/16" socket and breaker bar, on the jackstand, as before. Now you'll use the breaker bar to put 300 ft/lbs of torque on the nut -- the breaker bar is a simple lever, 300 ft/lbs is a 150 lb person standing on the end of a 24" (2 foot) breaker bar -- 2 * 150 = 300. Turn it further, just enough to put a new cotter pin in the hole. I have to bounce on the end to tweak it into place.

Repeat the other side, and you're done.