Over the weekend, I decided the time had come to replace the left front driveaxle in my old Jeep. Mainly because the CV boot was torn open and slinging grease all over the place. It’s a 93 Jeep, back when Jeeps were actually off-road vehicles instead of the minivans with big wheels that they are today. As such, it has solid axles (rather than independent suspension), which are much better for going over rocks, and also much better at shaking your fillings loose every time you hit a pothole (of which Rochester has many). “Solid” axles are in fact hollow, and the driveshaft spins inside of them. The driveshaft has only a single, outboard CV joint, instead of the pair found on the driveaxles of independently sprung vehicles. What this all means is that on a vehicle like the Jeep the only way to get the driveaxle out is to pull off the hub, for which I use the Mother Of All Tools (see below).
The first step is to get the hub nut off, a job which can vary in intensity from “obnoxious” to “epic”. At 36 mm, the hub nut is the diameter of a medium-sized dinosaur’s brain, and is supposed to be torqued down to a tyrannosaurus 175 lb-ft. And if that doesn’t bite sufficiently, it’s further secured by an oversized, rusty cotter pin. With that ADX Florence-worthy security, you might well wonder what baleful thing would happen if that hub nut were to escape at highway speed. Pretty much nothing, as near as I can tell. The hub actually engages the axle through a set of splines; the nut is just for decoration.
What scores this job a minimum of “obnoxious” on the odium scale is that to get the cotter pin out, the wheel has to be off; while to de-torque that monster nut, the wheel has to be both on and resting on pavement. You guessed it: you have to jack the Jeep up, take off the wheel, pull the cotter pin out, put the wheel back on, lower the Jeep, crack the nut loose, jack the Jeep back up, take off the wheel, and finally un-thread the nut. And when you’re all done, you get to do all that in reverse order to put it back on :) The cotter pin came out with some combination of pliering, hammering, and using a screwdriver for its unintended purpose, while the nut broke loose with a satisfying “crack!” and a little help from my 2 foot breaker bar. Then I could move onto the hub.
Well, not quite. The brake caliper came off without a fuss, and I wired it up to the coil spring to keep it out of the way. But then the brake rotor, which is supposed to more or less fall off at that point, didn’t. I had to break out my slide hammer a bit earlier than anticipated. With a few knocks, I successfully amputated the brake disk.
With the prep work done, I could get to work on the hub. The hub was originally held on by three 12-point bolts and a whole lot of friction. 17 years later, it is held on by three 12-point bolts, a heavy caking of rust, and a whole lot friction. I began my assault on the rust early with a heavy barage of WD-40, then moved onto the bolts. The heads were so corroded, it took me about 5 minutes to even figure out what tool was supposed to go on them. It turned out to be a 13 mm 12-point socket or box end wrench – you know, that one you never lose (because you never take it out of your toolbox). I started with the box end, and with sufficient hammering, got it on the first bolt. I pushed down on that itty-bitty wrench handle as hard as I could, which made a big impression on my palm, but none on the bolt. I tried the double-wrench trick I learned from my brother,
but still nothing. Time for some bigger tools.
Trouble here is that the bolt heads are facing in, toward the differential, and there is not much clearance between the hub and the steering knuckle for large pieces of steel. I have but one (very shiny and well-preserved) 12-point 13 mm socket, which has a 3/8 inch square hole on the receiving end. Now a 3/8” breaker bar is one of the few tools I’ve never invested in, though I’ll admit my 3/8” torque wrench has stood in in that capacity a few times. What I bought instead was a 1/2 – 3/8” adapter, which is usually sufficient.
But the stack of socket + adaptor + breaker bar head simply wouldn’t fit between the knuckle and hub. My 1/2” ratchet handle, which is about 4 times shorter than the breaker bar, would. Well, at least the handle is padded… Then I pushed, pushed, pushed, the kind that leaves red spots in front of your eyes. I have to admit, I was pretty surprised when that first bolt actually broke loose, sending bits of rust flying – I thought for sure I would feel instead that sickening slow give as chrome-vanadium steel gouges away carbon steel, turning a 12-point bolt into a carriage bolt (with no nut on the far end). In retrospect, I give Chrystler credit for putting 12-point bolts there. Had they used hexagons, they would most certainly be circles now, and I would be up a creek. A portrait of the heroic bolts is below.
The purpose of those three bolts is to press-fit the hub into the round metal piece that I will scientifically call the “hub-holder”. Alas, removing the three culprits does nothing to alleviate the press-fit, now reinforced with a generous serving of rust. That’s where the Mother Of All Tools, my 13 pound slide hammer, comes in. The beak-like thing at the end goes behind the hub, and you smack that big grey weight onto the opposite end of the tool with as much force as you can muster. Now most car parts – actually, most parts of anything – won’t stand up to that sort of treatment; but fortunately, hubs are tougher than nails. In fact, hubs could grind nails back into three pennies, or whatever it is that they are made of. I smashed and smashed that hub, turning occasionally, and it pretended like nothing was happening. But I knew better. Ever so gradually, a hairline gap opened up between the hub and the brake dust shield, then a three-penny gap, then the hub plopped out on the ground.
Actually replacing the driveaxle was almost anti-climatic. I pulled the old one straight out of the hollow axle, through the now-vacant hub-holder, and lined it up with the new one to make sure Auto Zone had sold me the right part (always a good idea). The problem with the old one should be obvious. Lacking gear oil (my least favorite automotive fluid, with a smell I find totally nauseating), I coated the inboard splines on the new one with some motor oil, then slid it in. One curious thing is that there does not seem to be any bearing at the outboard edge of the axle tube. I guess Jeep just relies on the splines in the differential to keep the shaft from smacking the insides of the tube (that, or the old bearing disintegrated and fell out, in which case I’ll get to do this all over again in the near future). Reassembly is the reverse of disassembly (tautologically so).
Overall, not a bad project. One of those projects that amazes me at how strong bolts are, even when they look like they are coming off the Titanic. How can I still be amazed at how strong bolts are, after 10 years of working on cars? Because the other half of the time I am amazed at how *weak* they are, snapping off or stripping at the slightest provocation. Regardless, any day I get to take my 13 pound slide hammer out of its oversized case is a good day. Because when you’ve got a slide hammer, the whole world is a hub (and hubs are tougher than nails).
Did you find a typo in the post? Let me know here.