Wow, that really sucked.
I just finished replacing the axle boot on my '64 230SL and it was one of the more difficult and frustrating jobs I've encountered. I read through the many posts here covering how to do it, and wanted to add my experience to the pool of knowledge because what I encountered wasn't much like what others described.
First, if your boot hasn't been replaced, check it because I can pretty well guarantee it's compromised. And it's not just about leaking oil, in fact leaking oil is probably the least troubling side effect of a damaged boot. It will also allow dirt and water into the rear axle which is definitely not good.
I've been avoiding mine for years, but the car hasn't been on the road so not a big deal. It's just good old fashion procrastination. I have even had the replacement boot on hand for years, but I have dreaded the job, so avoided it. But now the car back on the road (yippie), so needed to fix it.
First let's talk about access. It's not good. Many people have suggested removing the gas tank, and I think if you do not have a lift or good jacks then I can see how this would allow the job to be done from above rather than below. But I have a lift which gives about as good access as you can get, and with it I don't think removing the tank would have been any help.
What is definitely in the way is the compensator spring. At first I left it in place because my spring compressor wouldn't fit in there, and I didn't see any practical way to remove it. I got the old boot cut out and removed, and did some test fitting of the new boot trying to sort out how I was going to approach installing it, including sealing and installing the metal clips. While I was doing this I realized it was going to be a very difficult job unless I removed the spring.
I read here that if you disconnect the shocks and let the axle halves hang down to their max, that there is very little tension remaining in the spring and it can be removed one bolt at a time, carefully swinging the end plate clear. Well that wasn't the case at all on my car. Not even close. When I removed the first bolt, the whole thing exploded out of the car in a way that kills mechanics. It was not a happy moment, though actually it was because I escaped any injury. The bottom line is that there was still a good 3-4" of compression on the spring. Maybe my car is different, or maybe others have developed a technique for removing the spring, by my recommendation is that the only safe way to do it is with a spring compressor of some sort. You just need one that can fit into the space.
Next is the boot. The new boot hasn't been stretched out for 50 years, so is in a collapsed state. That makes it hard to stretch it from one tube to the other without it popping back off in the process. And with the shocks removed and the axles drooping to their max, it simply won't span the gap. So the only way to get the new boot on is with the axles at least back on the shocks.
Now to complicate this further, once you get the new boot on, I was worried about busting its seam if I allowed the axles to droop back down again. At that angle it's not just drawing out the pleats in the boot, but actually stretching the rubber. I didn't want to risk blowing it out. But to have any hope of reinstalling the compensator spring the axles need to be in full droop, which means the spring needs to go back on before the boot is stretched to span the tubes, and there goes the access that you hoped to gain by removing it in the first place.
So what I decided to do is assemble the boot with the spring removed, including securing it to the axle tube. Then reinstall the spring, raise the axles back up and hang them from the shocks, then pull the boot over the differential and secure that end. All without busting open the seam in the boot.
My replacement boot, since I've had it for so long, came with the staples rather than the hog clamps or whatever they are called. On the work bench I sorted out pre-bending the staples to ease installation, and leave as little crimping as possible in the confines of the actual installation. I settled on completely pre-bending one end of the staples, then a partial bend on the other end. The idea was to hook the pre-bent end over the boot half furthest away from me, then pull with pliers and hook the partial-hook end over the near half, with the partial-hook holding things in place. Then I could reach in the pliers to complete the near-side crimp. With all the clips prepped, it was on to the actual installation, but first a quick aside.
On my car, and probably others that have been leaking back there, there was a pretty good coating of oil and grease residue. But this stuff had distilled down to a tar-like substance unlike anything I have encountered before. I got a bunch on my arms and is just wouldn't come off, instead balling up in little tar balls. I ended up using brake clean to get the crap off of me, and that's not my first choice for bath soap. So beware and wear a long sleeve, disposable shirt because you will be reaching up, over, and around the differential while you do this job.
OK, back to the boot. I decided to use weather strip adhesive in addition to the staples. More boots are reported leak-free using some sort of glue, so that's what I did. I used a small paint brush to paste the seams of the joint, let it tack dry, then stuck it together. Then, with clips all prepared and ready to go, I stitched it up. By the way, I did this with both ends of the boot off of the axle tubes. I was going to install the axle end now, and the diff end later, but I wanted to fully glue and secure the seam before stretching it over the axle. I considered joining the seam with the boot already over the axle, but earlier trials suggest that wasn't going to go well, and at a minimum would get glue between the boot and axle. So I stitched up the seam with the boot off of both ends, then stretched the boot over the axle end. This worked fine and I was able to clamp that end in place, making sure the seam was at the 9 o'clock position looking from the right side. This part went well, and I left it to set up over night while I contemplated re-installation of the spring.
My first thought was to do as others have described which is to use the spring end bracket with one bolt installed plus a pry bar as a sort of hinged compressor, but that was a non-starter. The uncompressed spring was way too long for the bracket to get a bite on it. There was just no way. So next I used my spring compressor which is actually two compressors, one for each side of the spring. I figured if I could pre-compress the spring enough I could then get the hinged end bracket on, and finish it off with a lever bar. The trick was to locate the compressor so I could then get it out afterwards, and so it wouldn't bottom out on the diff or other structures. With some fussing, I got the spring compressed enough to then apply the "hinged end plate" technique. With a pry bar plus a 4' extension pipe, I was then able to pivot the end bracket and compress the spring far enough to get the second bolt in the bracket. It was a bit nerve wracking, especially since I hate putting significant side loads on a car when it's on a lift, but it worked and the spring was back in place.
Now all that was left was getting the boot pulled over the diff end and secured in place. First I jacked each wheel back up and reinstalled the shocks. This reduced the axle droop enough so installing the boot was plausible. But still, to go over the diff end, the bottom of the boot would be completely compressed, and the top completely stretched. If the whole rear end were lying on the floor you could straddle the thing and pull the boot into place. But in the car it's a lot harder, and when you get one part on, the last part you got on wants to come off again. Having three or four hands would help, but even without them, I was finally able to get it on, and thankfully the lip on the diff is enough to keep it from popping back off a gain. Last step was to install the band clamp.
Then the car came back down on the ground and rolled back to the apron entrance to my shop. If you stop with the rear wheel still on the shop floor, the apron drops off and gives good space to get under and fill up the diff oil with the car on flat ground. Oil full, and job done.
Man, I hope it doesn't leak.
For those of you who have had an easier time of this, please add whatever tips you can. Others will benefit, and I still have another one of these to do. -:(
