How to Replace a W108 Steering Coupler Without Dropping the Steering Box - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 10-10-2011, 09:53 PM Thread Starter
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Vehicle: 1966 250S
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How to Replace a W108 Steering Coupler Without Dropping the Steering Box

After scouring the internet and seeing repeated hints on forums that it might be possible to change the steering coupler on a w108 (and likely others) without detaching the steering box, I then spent a lot more completely fruitless time trying to find out how to actually do so. Finally, I decided I'd rather tinker around on my own and try to figure it out than to go through all of the headaches and bruises everyone seems to unanimously report when trying to reassemble things after dropping the steering box.

I won't say that I didn't get a bloody knuckle (two, actually) but I'm happy to report that I was able to figure it out and managed to pull my steering coupling to clean it and replace the bushings (actually that should be "install the bushings" since the old ones had completely disintegrated and were long gone) and then reinstall it without having to touch the steering box or even lift the car. I'm new to this forum and I'm new to the joys of owning a classic Benz, but I've already gotten a LOT of useful information from you other users here, so I thought I would try to do my part and describe this procedure for anyone looking to do it in the future.

Caveat: My car is a 1966 250s with a floor shifter, and I've never even looked under the hood at one of the bigger engines or examined a column shift in one of these cars, so if you have less space to work with under the hood take this with a grain of salt and if you have a column shift... you'll have to figure that part out on your own.

Essentially, the trick is to go at it from the opposite side of things than most people describe, by pulling the column into the car several inches to create a gap big enough to slide the coupling off. I was able to do this by first leaning in under the hood to remove the two hex bolts from the coupling (this was the hardest and knuckle-bustingest part of the procedure) and then gently-but-firmly prying each of the halves open enough with a flat-headed screwdriver that they were able to slide up and down on their respective shafts. This isn't really even prying them "open," so much as just prying on them a bit bit to loosen them up. I then removed the clips and washers from the coupling and slid the halves as far apart as possible.

From this point on, I was on my own, so there was a fair amount of trial and error and going back and forth from the driver's seat to under the hood. I also wasted a lot of time in an uncomfortable position trying to loosen the steering column housing from the firewall because someone had written that someone else had said that it was possible to go about it that way. That may well be, but it's probably not any easier to do that than dropping the steering box. After I'd managed to loosen a few bolts on the housing I realized that I would have to pull the dash or risk damaging it in order to get the housing loose enough to affect the column by the coupling thanks to the retaining bracket near the top under the dash, so I decided to quit trying and focus on the shaft itself, within the housing.

First remove the steering wheel by gently pulling the emblem pad off to reveal a big nut, and then removing the nut and pulling the wheel free. Then remove the horn button mechanism behind it (metal ring mounted in plastic). It should just pull out. There's no need to remove the nut from the one visible bolt... which I didn't realize til I'd already done so. The horn button is attached by two wires, but there should be enough slack to just push it to the left side, out of the way. Behind the horn button are two hex bolts. Remove them. Then remove the rubber housing around the base of the turn signal shaft. It just pulls out with a gentle tug. Underneath there are two screws. Remove them and let the turn signal dangle by its wires.

This is the point where having a column shifter will probably require you to do some exploratory surgery on your own... unless it's attached to the outside of the column housing, in which case you might be fine. I have no idea.

Now that everything is ready, gently wedge a flat headed screwdriver between the end of the painted metal housing and the lip of the cast metal that surrounds the column where it comes out of the housing just behind where the steering wheel usually is. You should be able to work it loose without much effort. Once loose, you can pull up (meaning towards your chest when sitting in the driver's seat) on the entire column assembly by probably three inches without hitting resistance. If you look under the hood after doing so, you'll see a three inch gap between the pieces of column that the coupling is designed to bridge. This should be large enough to slide the pieces of the coupling off one at a time.

The usual warnings about being careful about alignment when removing/reinstalling the coupling apply here... it's easy to be off by a spline or two and throw your steering wheel alignment out of whack. And you can't just plan on correcting for it when re-mounting the steering wheel on its splines, because that would leave the turn signal cancelling mechanism off-center, which would be annoying at best and dangerous at worst. I was able to mark the shaft and reinstall the coupling correctly, and then I corrected a very slight misalignment in the steering wheel that was already present from a previous owner's work (he painted the metal bracket that holds the horn ring to match new seats in the car) when I put the wheel back on, so now it's straighter than ever.

Reassembly is all the same in reverse.

My steering is much better now than it was and having bushings back in that coupling has removed a lot of clanging and clicking noise coming from the shaft. I still have more play than I want to and will have to chase that down through the box and beyond, but that's next weekend's task.

Best of luck!

Last edited by Elwood911; 10-10-2011 at 09:57 PM. Reason: Factual correction
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post #2 of 3 (permalink) Old 10-11-2011, 09:35 PM
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Thank you for the post. I am in the process of doing the exact same thing to my 1972 280 SE 4.5 (108). I am also converting it from a column shift to a floor shift.

Sherif Tewfik

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78 6.9
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post #3 of 3 (permalink) Old 10-11-2011, 09:57 PM Thread Starter
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Date registered: Sep 2011
Vehicle: 1966 250S
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Good luck tewfiks! I hope it all goes smoothly.

I've heard of people changing column shifts to floor shifts several times before on forums, but never the other way around. If you don't mind my asking, what's the point of the change? Is it just that floor shifters are more common and/or modern and are therefore easier to use, or is there some other benefit I'm not aware of?
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