W123 300TD 300D Front Shock Change Tips - PeachParts Mercedes-Benz Forum

phidauex · #1 11-05-2005, 01:55 PM

Just putting this out there for the searchers and people hoping to do this work soon..

I just changed the front shock absorbers on my 123 '82 300TD, and wanted to give a few tips.. Sorry, no pictures. The process should be identical on a 300D or 300CD.

The first is, the job is really quite easy. I did it in 3 hours in the middle of the night on the street, and it was my first shock change ever. The first shock took two hours while I figured everything out, and then the second shock took half an hour.

I was replacing a set of KRAPPY gas-a-just shocks that someone had installed in the distant past. They were loose, rusty, and gross. When I bought the car a year ago the guy said, "Oh, btw, the shocks are shot." and I said, "Oh well, don't have the money to fix it" and just lived with the ride, which I thought was pretty good anyway. Well, now I know that the ride was NOT good. The new shocks are very different, and the car is much more confident now. I realized that I had been subconciously avoiding bumps in the road by swerving around, and now I can just roll over them without bouncing like an old buick. A lot less roll in corners, and less nose dive as well.

The old shocks were really loose, and one was about 6" shorter than the other, fully extended, which probably explains why my car would sometimes dive to the right when under heavy braking. That tendency is now gone!

I bought Bilstein Comfort shocks, part number B36-0703. I got them from http://www.adsitco.com who has them (brand new) on sale for 49$ right now (thats right, less than most of the crappy shock brands!). By all accounts, these are the best possible shocks for the wagons, you won't find anything better, and at that price, there is no reason not to go premium. The sale won't last forever, so if you are reading this in the future, go to Fastlane, since they have very reasonable prices on these shocks as well (and Phil is a good man).

The basic procedure:

1: Loosen the lug nuts on the front wheels. Don't remove them, just break them loose so you don't have to tug on them with the car lifted.

2: Put the car up on jack stands. I use the frame rails under the car, and put a block of wood between the stand and the rail to soften it up.

3: Remove the wheels, and lift the hood.

4: The top of the shock shaft will extend into the engine compartment, and be held in place by either a nut and a locknut, or a self-locking nut (a nylock nut), depending on what is under there now. Remove the locknut and the main nut, or just the main nut, and remove the washer and rubber bushing. When the nut is removed, the suspension will sag a bit (but don't worry, the spring can't release on the 123 body, though the 124 I believe must be supported with a sturdy jack under the control arm to prevent the spring from flying loose).

5: From the wheel well, remove the two 10mm 12pt bolts holding the bracket of the shock in place. One bolt is more accessible with the steering wheel turned one way, and the other bolt is more accessible with the steering wheel turned the other way, it'll be obvious when you are in there which is which. There is also very little clearance against the shock itself, so you may have to arrange for a very thin box-end wrench to remove the bolts. Spray these down with PBlaster or another penetrating lubricant before hand, since they have been torqued down pretty good.

The reason we released the top of the shock shaft first is that you can now compress the shock a bit (it'll take some force, but you can do it, especially with an old shock), and then lean the shock in or out a bit to provide better access to these bolts.

Because there is little clearance, I had to use a small 10mm box wrench instead of my sockets. If your wrenches are on the thick side, you may even need to grind it down a bit to slip into the tight space. That is the hardest part of the process.

6: Once the bottom bolts are removed, slide the entire shock tower out, it will come out easily.

7: The Bilstein shocks I bought from Adsitco included in the package the bump stop (a yellow foam cylinder that slides over the shock shaft), and a dust cover (a big rubber cylinder that fits over the shaft, and part of the tower), as well as new 12pt bolts (with lock washers), new rubber bushings, new washers, and a new nylock nut for the top. If your shocks don't include any of these pieces, expect to harvest them from the old shock, or buy a shock mounting kit from the dealer.

8: Slide the bump stop, then the dust cover, then a washer (cup facing up), and a rubber bushing (flat spot up) onto the shaft, and put the new shock tower in place. Don't worry about putting the shaft through the hole in the frame yet, focus on getting the lower bracket in place. Finger tighten the two bracket bolts, tipping the shock in and out on its pivot to allow better access, and turning the steering wheel from one side to the other to allow better access. I did the inner bolt first, then adjusted the wheel and shock position, and did the outer bolt second. Once these are both torqued down (you'll have to guess, I couldn't get my torque wrench in there, just snug them down as good as you can), compress the shock, and as it re-expands, guide the shaft through the hole in the frame. It will be tough to compress, but I only weigh 120 pounds, and I could do it, so you can too.

Double check that you have the bump stop, the rubber cover, the upward facing cup washer, and the rubber bushing (in that order) on the shaft before continuing. If you forget (like I did the first time), recompress the shock, and install those parts.

9: Once the shaft comes through the hole, install the other rubber bushing from the top (flat side down), then the other cup washer (cup facing down), and then the nylock nut. You may have to really press the washer down to compress the bushing a bit to get the nut to thread on. Give it a few good turns (don't crank it down), and move on. You may need to immobilize the shock shaft with a 7mm wrench on the flats shaft (at the very top) to prevent it from turning as you tighten the nut.

10: Once you have done both sides, reinstall your wheels (but don't torque the lug bolts down yet), and lower the car to the ground. Like all suspension components, you torque brackets and 'fixed' components while in the air (like our lower bracket), and torque flexible things like bushings with weight on the suspension.

With the car on the ground, you should torque your lug bolts to 90ft/pounds while you are thinking about it.

11: Now you can torque the nylock nut on the top of each shaft. Do NOT crank this down! Technically speaking, it should only be torqued to 19 ft/pounds, which is not much at all. You may not be able to use a torque wrench, because the shaft must be immobilized at the top with a wrench to tighten the nut, but just keep that number in mind. 19 ft/lbs is not much. What you should aim to do is get the nylon part of the nut fully on the threads, with maybe one or two threads exposed above it. The total exposed nut+shaft, above the washer, should be 24mm. If you crank this down too hard, you'll smush the bushings, and they won't do their job.

12: Close the hood, make sure you torqued your lug bolts, and take your car for a quick test drive. Feels, nice, don't it? When you stop, take a gander at everything, and make sure it is all still secure and snug, especially the lower bracket bolts. Then have a beer, you are done.

Hope this helps someone! For less than 100$, these nice shocks are the best suspension improvement you can make for the money. My ride height looks perfect (not too high or too low), and with my functioning rear SLS (though it does have a tiny leak at the pump now...), the ride on this car is really good. Just like a Benz should be.

peace,
sam

phidauex · #2 11-07-2005, 04:02 PM

Just an update, after a week of operation, the shocks have settled in nicely, stayed properly mounted, and are a real pleasure to drive on. Damn, I love my wagon.

peace,
sam

Mister Byrnzoil · #3 05-08-2007, 08:00 PM

great post, good reading, bump worthy