I'm Bushed

Well, it wasn't 102 like yesterday, but it was a pretty hot one here at about 96. Around 10 AM, as it really started to warm up, I decided to take on a couple of simple W126 300SD repair tasks: steering damper replacement, and shift bushing replacement. These are both conceptually simple jobs, and replacing the steering damper is even simple in actuality. The shift bushing replacement is a little trickier, but I had purchased a parts kit that made it at least reasonable.

A steering damper is just a shock absorber designed to be installed horizontally, and in this case it's held at each end with a bolt with a 17mm head, with a nut which also takes a 17mm wrench. If you have a 17mm gearwrench (or similar) and a 17mm normal wrench this job will practically do itself. My old damper gave no discernible damping, even when removed it slid freely. It will be interesting to drive the car again and feel the difference.

The bushings for the automatic transmission shift arrangement on all Mercedes from 1969 to 1995 are identical, and the general arrangement of parts is usually the same. On the W126 there is a floor shifter with a patterned gate, and no button on the shift lever. The shifter communicates with the transmission via a hard linkage threaded at the shifter end for adjustment. At each end of the linkage there is a soft nylon bushing through which the linkage passes. On the shifter end, the end of the shift lever simply passes through the floor, terminating in a flat piece with a hole to accept the bushing. The linkage is held into this bushing via a stamped spring clip at each end, but you can substitute a washer and a C-clip if you lose the original clip. At the other end there is an easily removable arm (via a pair of 10mm wrenches - again I used one gearwrench) with a hole in it, again to take the bushing.

As usual, the bushings are pressed into place. This is a somewhat tricky proposal. The easiest way to get access to the bushing on the transmission is to remove the shift arm. If you don't want to remove the shifter from the car, which is honestly probably your best bet, you'll have to have a fairly tricky little tool in order to install the bushing. You can simply purchase a pair of bushings and a nifty little tool from Mercedes Source, which is exactly what I did. I'm not going to provide any measurements, but it consists of a bolt, a nut, a couple washers, and a bigger nut being used as a spacer. The bushing is pressed through the hole and into the nut on the other side by tightening the nut, and you stop just at the right time, which for me was less than a dime's thickness of space left. When reinstalling the lever on the side of the transmission, you have to be careful to get the lever on the range switch back into the hole on the arm; the shaft that the lever rides on passes through it.

Getting the OE spring clip back on the end of the rod was the tricky part for me. The last time I messed with one of these I'm afraid I was lying underneath my last 300SD, an '81, in a bank parking lot messing with it with a Gerber Multi-Tool while holding a Mag-Lite in my mouth. The bushing at the shift lever had disappeared and the prior owner had replaced the original spring clip with a C-clip and no washer. The result was that the C-clip passed right through the hole in the shift lever, and naturally I lost the ability to shift at all. I found a ring terminal of a compatible size in my toolbag and managed to get down the road with a sloppy shifter, but it was not an experience I would care to repeat. But, on the topic at hand; the insertion of a medium-sized slotted screwdriver into the rounded end of the spring clip will hold it open sufficiently that you should be able to get it onto the rod. I used a small wedge of wood to jam the linkage into the bushing and hold it there so that I could apply pressure to its end while installing the clip. I used this same tactic at each end of the linkage, except that I actually used a cheap 1/2 inch ratcheting wrench on the shift lever end -- the same wrench I used to tighten the installation tool on the bushing.

Aside from these tools this job also involved some penetrating Loc-Tite (green) and my fluorescent shop light, both of which are pretty much mandatory, as well as some short jack stands I picked up at a yard sale for three bucks. While they are not flat-topped, they have holes in them, so I imagine cutting the ears off and installing some kind of plastic pucks1 on top of them eventually. However, one of the ears was already bent flat on one stand, so I simply altered the other for now by the simple expedient of whacking it with a drilling sledge. With one ear bent down they fit nicely underneath the rubber pads on the chassis and don't touch anything else, as long as you leave the un-bent ear towards the outside. This provides a much less scary situation for work than laying under the car with one wheel chock and the e-brake to keep you from certain death should the car pivot on the factory jack, with its rounded foot. I also own ramps, but those have been known to collapse on occasion and I only use them when there is no alternative.

While I was down there I discovered that the part of the oil system that the pressure gauge taps into has a slight leak, so that goes on the list of things to do at the next oil change, what fun. I have the gasket here someplace already. I recently discovered also that one of the screws in the driver's door latch adjustment (the part the latch locating pin goes into and that the latch grabs onto) is jammed by stripping out the head, which uses a hex screw. The others all came free with liquid wrench with silicone, but that one is going to need to be drilled out, extracted, and replaced. Hopefully I'll be able to get an extractor to bite the head of the screw without really doing much but just beveling the bottom of the hole. It would be nice to have my driver's door close smoothly.

  • 1. Probably not literally hockey pucks, which are known to break.

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