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Saturday, July 16, 2011
The Puller & The Pullee, the Back Story
Big, ugly axle nut
A long time ago I was living in Houston and I had Rambler station wagon in my care that needed new rear brakes. I was working as an industrial mechanic at that time, so it was no big deal, or so I thought. On most cars the rear brake drums are secured by the lug nuts that hold the wheel on. The end of the axle has a flange with the wheel studs, the brake drum is sandwiched between the wheel and this flange, and the lug nuts hold the whole thing together. Not this Rambler though. The end of the axle is threaded and there is a big nut holding the brake drum in place. That would be okay, if I could loosen it, but no matter how big a wrench I put on it, I could not get it to budge. I finally ended up using a cold chisel to cut one side of the nut. Only then was I able to unscrew it.
Brake drum puller
Now we should be able to just pull the brake drum off. Um, no. It's going to take a wheel puller. Back then (the mid 1970's), a stout wheel puller was an expensive item, so I elected to rent one. The one they gave me had a weld across one of the legs. This doesn't look good. The thing has been broken once, and somebody has welded it back together. Oh, well, it's got to be better than tugging on it with my hands, so I take it home and give it a try. Bang! It breaks. So it's not any better than my hands. Eventually I got the drums off. The axle and the hole in the drum were a Morse taper (see picture), so I think the technique for separating them is to tighten up the wheel puller to put some strain on the brake drum, and then wack the end of the pulling screw with a big hammer. With luck, this will break the grip of the taper, and the whole thing will come off in your hand.
Rambler rear brake assembly and axle
So I got the brake drums off, replaced the shoes, and I am putting things back together, but I need two new axle nuts, after all, I split the old ones so they aren't going to work anymore. So off to the auto parts store I go where I search hi and low for the right axle nuts. I find two that match the ones I took off, but they are not the same diameter as the axles. I root around some more and eventually find two more that are the correct diameter (and thread pitch) but they do not use the same size wrench. I take them home and they thread onto the axles like they were made for it. What's going on here? The difference in diameter of the two nuts I found was on the order of a sixteenth, or maybe a thirty-second of an inch. I think what happened is that the last time this job was done, somebody gave the mechanic the wrong axle nuts. Not having the right ones, wanting to get the job done and go home, he heated them up till they were red-hot and then ran them on with an impact wrench, where they cooled, contracted, and became one with the axle. I can't imagine how else this situation could have come to pass.