Here's a great example of a project that has undergone a bit of "feature creep". Oh, it started innocently enough, with my wife asking if anything could be done to improve the brake feel of our 1996 Buick Roadmaster. Sure, I said - we can ditch the rear drum brakes, and install a set of discs from either an Impala SS or a Caprice 9C1 (the infamous "cop car" version). That task would be easy to pull off in an afternoon or two.

About five minutes of searching on eBay turned up a complete set of used Impala brakes, but our $200 maximum bid wasn't enough to secure the parts. A little more browsing turned up a complete used Impala SS axle, with 90-day warranty, for $349. That'd allow us to upgrade the Roadmaster's extra tall 2.56:1 rear gears with the Impala's somewhat more reasonable 3.08 gears, and if the used axle's limited slip still functioned properly after 86,000 miles, it could replace the absolutely shot Auburn that wasn't doing a damn thing to keep both of the Buick's rear tires spinning together. A click on the Buy It Now button, a bit of correspondence, and the axle was on its way to a local shipping depot.

When the axle showed up, it appeared to be in decent condition; there was a bit of surface rust, but certainly nothing like we'd expect to see here in the Midwest after a decade of use.

The first step, obviously, was to move the axle from the back of our parts hauler and onto a suitable work surface (actually, sometimes those are one and the same, but not this time around). Our motto around here is "lift with the tractor, not with the back". The shipping weight of the axle is about 290 lbs, so it can be carried by two people should one lack a front-end loader or forklift.

With the axle on the bench, it's time to start tearing it apart. The disassembly starts by removing the calipers and brackets, at which point the discs can be slid off the axle.

With the diff cover removed, the next step is to remove the differential cross pin. First we remove the retaining bolt with a 5/16" box wrench (a socket won't fit in here), and then a few light taps with a hammer and punch drives the pin right the other side.

Next, we give each axle shaft a light swat with a sledgehammer to drive them in towards the center of the axle. This frees the C-clips from the side gears of the differential.

I'm not quite sure what we were doing with the gasket scraper in this shot, so I'd recommend just ignoring it (whatever we were doing, it had nothing to do with scraping gaskets).

The C-clips are then removed. A magnetic retrieval tool is usually handy here, as it can be difficult to grasp the clips with greasy fingers.

The axles can then be pulled out of the housing and set aside.

Next, the differential carrier bearing caps can be removed. Since the caps are usually side-specific, mark them or separate them in some manner that will allow them to go back into their original location.

With the caps removed, the diff carrier can be removed. Sometimes it requires a light amount of prying with a prybar or large screwdriver. There will typically be a shim on each side, and this is location-specific as well (they locate the carrier laterally and are responsible for setting the gear backlash). Keep them separate or mark them with a grease pen or some tape.

With the carrier removed, we can see the pinion gear. To remove it, swing around to the other end...

...And hit the pinion yoke nut with an impact wrench and large socket (1 1/4" in this case). It's highly unlikely that one will be able to remove this nut via the use of hand tools, although we have once before been forced to remove it using a large breaker bar and several smacks with a sledgehammer. Since it can't go back together that way (more on this in an upcoming post), make sure that an impact wrench (electric or air) is available.

With the yoke nut removed, the yoke can be removed via a few smacks to the pinion. Use a sledgehammer and a brass punch, or hit the nut and not the pinion itself. The nut will be discarded, and a new one will be installed upon reassembly.

Remove the pinion seal with a seal remover (shown) or a prybar. Discard the used seal.

Remove the pinion bearing and set it aside for cleaning and inspection.

Now, we move back to the ends of the axle housing and remove the axle seals. Discard the old seals, of course.

The "right" way to remove axle bearings involves way too much time spent stroking a slide hammer. If the bearings are to be replaced - and indeed we will be doing exactly that - a length of pipe slid through the housing to the other side and a few swings of a sledgehammer will remove the bearings with far less effort. Do not use this method if the bearings are to be reused. In fact, if the axle bearings are to be reused (not a great idea, in our opinion, since they're usually the most likely to fail), it's probably best just to leave them in place.

The parking brake assembly and cables are removed for cleaning and inspection.

We then removed the rubber brake lines and steel brake pipes. The rubber lines will be discarded, while the steel lines will be cleaned and inspected.

Finally, remove the ABS speed sensor for cleaning (this also provides access to the lubrication channel in the nose of the diff housing).

That takes care of the teardown process. We spent approximately two hours to get to this point, and about half of that was running back and forth between the garage and the barn to gather the right tools.

In the next installments, we'll walk through some of the cleaning and prep work, reassemble the axle and brakes, and then finally we'll get it installed under the back of the big Buick.


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