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  #1  
Old 10-11-2020, 12:14 AM
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Rebuild Front End Suspension on 1985 W123 300CD

Hello everybody,

I have developed very, very heavy vibrations when going over about 40-45 MPH in my 1985 300CD which I purchased about 3 months ago (180k+ miles). Appears to be coming from the driver's side front end. As a total amateur, I am still learning my right hand from my left, and assume that this is one or more worn front end suspension components. I have not jacked anything up yet, but had a quick look underneath and there are definitely some worn out bushings immediately visible.

I have been doing a deep dive on youtube and seen many promising videos on rebuilding a front-end suspension. Rather than replacing the culprit part, I am assuming I'm probably better off replacing everything with high quality parts while I'm already down there, instead of waiting for other components to fail(?).

That said, a lot of the threads I've found are quite old, and I'm wondering if anybody can steer me to kits that would be helpful/ cost effective (if any exist). Has anybody tackled this job recently? Any nuggets of advice would be greatly appreciated.

Thanks!!
-RJ

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  #2  
Old 10-11-2020, 12:21 AM
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Someone recently had car vibration issues and found it was a bulge in his Tire causing it (in fact low tire pressure on one side can cause vibration). Start off with the basic stuff that does not take a lot of invasive actions first.

This could be a repeat but there is no high quality parts kit that I know of.
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Last edited by Diesel911; 10-11-2020 at 12:39 AM.
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  #3  
Old 10-11-2020, 12:25 AM
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Quote:
Originally Posted by Rmagoon1990 View Post
...I have developed very, very heavy vibrations when going over about 40-45 MPH in my 1985 300CD ... Appears to be coming from the driver's side front end... steer me to kits that would be helpful/ cost effective...
I won't steer you towards any kits but I will tell you what you can check for exactly zero dollars:

#1: check for loose lug bolts, also if there are any weird wear patterns on the tires

#2: safely get under the vehicle and either look or take a picture of your: both flex discs and the center driveshaft support mount

#3: condition of your tranny mount? axle mount? rear subframe mount? they can all affect the driveshaft angle
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  #4  
Old 10-11-2020, 12:36 AM
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Quote:
Originally Posted by Rmagoon1990 View Post
Hello everybody,

I have developed very, very heavy vibrations when going over about 40-45 MPH in my 1985 300CD which I purchased about 3 months ago (180k+ miles). Appears to be coming from the driver's side front end. As a total amateur, I am still learning my right hand from my left, and assume that this is one or more worn front end suspension components. I have not jacked anything up yet, but had a quick look underneath and there are definitely some worn out bushings immediately visible.

I have been doing a deep dive on youtube and seen many promising videos on rebuilding a front-end suspension. Rather than replacing the culprit part, I am assuming I'm probably better off replacing everything with high quality parts while I'm already down there, instead of waiting for other components to fail(?).

That said, a lot of the threads I've found are quite old, and I'm wondering if anybody can steer me to kits that would be helpful/ cost effective (if any exist). Has anybody tackled this job recently? Any nuggets of advice would be greatly appreciated.

Thanks!!
-RJ
If you are in the UK the drivers side can be different then the US. Left and right is determined as if you are sitting in the drivers seat.

In the US the right side front is what typically gets the beating hitting the curb during parking.

I am curious to know if you are having unusual Tire wear patterns.

There is no kit with high end parts.

Some items like the Lower Ball Joints if they are still good can last another 5-10 years if the boots are kept intact and full of grease.

The lower and Upper control arms have rubber bushings that can have issues. The Upper control arms have the ball joint built in and when they go you have to replace the whole arm. New upper control arms have the new bushing in them already (be sure to check on that before ordering).

The torsion/sway bar has 2 rubber big O-rings on each side in the front where they go through the upper control arm. and there is also 2 rubber bushings on the fire wall that the bar pivots on.

Check your front wheel bearing end play and remember that a dragging brake on one side can also cause vibration.

As for the oldness of some of the threads all of the threads are newer then the Cars they are about and some of the older threads have not been replaced as they are still relevant.
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  #5  
Old 10-11-2020, 12:54 AM
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Yes, sorry I should clarify: Driver's side being on the left (American).

I should also clarify, I only brought up the age of the threads to see if any new kits had recently been offered, but it looks like if the front end were to be rebuilt it would be an item-by-item purchase anyway. I would never want to suggest that older threads are less relevant :-)

With regards to the tire, I should have also mentioned that I had a blow-out on the left front tire. I changed the tire and limped back home to be cautious, and for the past few weeks have been doing some body work in the garage so I haven't been driving it much at all. I took it out on the freeway again for the first time today and noticed the exact same symptoms at about 40 MPH. Replacement tire is mint and the lug nuts were torqued to spec so I'm assuming it shouldn't be the tire.

I will grab a flashlight and check out the transmission/axle/rear subframe mount as suggested and get some photos, as well as a more detailed look at the existing bushings. I should also research the dragging break as well.

I guess I should also add that these vibrations are INTENSE (shaking the whole car and not just the steering). When I had the blowout the vibrations started about 5-10 min before at +/- 65 MPH cruising speed. I'm assuming there is a correlation here, so I would be interested to hear any thoughts on this. Apologies, should have included this info in the first post! Thank you!
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  #6  
Old 10-11-2020, 09:56 AM
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Swap the tire positions see if it changes anything. Does it take a bump to get the vibration to start? Does braking change the vibration?
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  #7  
Old 10-11-2020, 12:13 PM
Grom
 
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Location: San Diego, CA
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I am looking at a front end rebuild as well, because I am also experiencing high speed vibrations.
However, a recently replaced my auto transmission mount (a relatively easy job) because it was worn out, and it actually helped with the vibration some. So, as others have suggested, look at your engine mounts as well.
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  #8  
Old 10-11-2020, 12:16 PM
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Hi All,

so I had a better look last night underneath the car. The bushings for the passenger right side look like they need to be replaced but are at least intact. The bushings for the driver's left side, however, are completely torn apart, one of which is basically non-existent. This certainly appears to be the culprit - or at least a likely starting point.

From everything that I've read and watched, it seems like replacing these bushings would be relatively intimidating for a beginner like myself, so probably best to pay up and have it done by a professional.

I was just curious for peoples' opinion on whether I should also have a) the ball joints replaced and b) the upper control arm assemblies replaced while this is being done? Also, is there a forum thread where somebody has compiled all of the rubber components most likely to fail or worthy of inspection?

Thanks again!
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  #9  
Old 10-11-2020, 01:00 PM
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All good points. Car is in excellent condition (bushings aside lol) and my goal is to ultimately use it as a daily driver. I have just never done anything like this and seen a few warnings of "don't try this at home."

However, I did also buy this car as a way to start learning how to do these things. I suppose I will re-phrase my question as how difficult is it to replace the lower control arm bushings on one's own with limited experience but a lot of research and patience, and if these are being done should the upper control arms and ball joints also be taken care of?

There are multiple tutorials online. Just want to throw this out there to see if there are any horror stories anyone has had!
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  #10  
Old 10-11-2020, 04:50 PM
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I have found problems with how "professionals" do things. Many take short cuts including not torquing correctly or stripping bolts. You can buy the tools and go to youtube university and accomplish most things.

I would replace everything related once you decide to go as far as removing the spring. Labor - even yours is much more expensive than parts. Buy quality parts. You don't want to do the job again in the near future. I think $500 was the approximate parts cost of doing the 85SD a few years ago.

Be sure to lube the threads of the spring tool or you'll damage it.
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  #11  
Old 10-11-2020, 06:12 PM
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Quote:
Originally Posted by Diesel911 View Post

There is no kit with high end parts.
One supplier offers this. Aftermarket, but at least not the elcheapo eBay kit

https://tinyurl.com/y3pso8gx

The link is from merc sauce and listed as 123 Chassis Lower Front Suspension Ultimate Restoration Kit. It doesn't include everything, but has a guide as to what may be needed.

On my 85, the ball joints and control arm bushings seemed to still be good (they have been replaced from time to time). We did put in new guide rod mounts and bushings and while about it, also new springs although there was really no need. Haven't done subframe mounts either, but they are a common item, but not for vibration.

For vibration, most causes have been mentioned. In my '85's case, causes were tires, tire balance weights off, wheel bearings, flex joints, motor and tranny mounts, drive shaft mid bearing.
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  #12  
Old 10-11-2020, 06:38 PM
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Remember loose components in the rear suspension also wear out causing wandering as the car begins to steer from the rear. If you cannot do a complete suspension rebuild now consider going to a Benz independent shop and have the car inspected to find out what is bad.

The front has both steering (linkages and rods) and suspension (arms, bushings, ball joints and springs) you could do the front steering and suspension separately.

Use the best parts available on the arms and ball joints, you don't want to do that part twice.

The two danger areas are the springs launching and you as the repairman forgetting to properly tighten something.

Good luck!!!
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  #13  
Old 10-11-2020, 07:27 PM
dkr dkr is offline
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Quote:
Swap the tire positions see if it changes anything
X2 on this. Did you try it yet? It could be a tire balancing issue.

I would say any time I hear someone has replaced their entire front suspension, it means they generally don't know what they are doing.

I have put hundreds of thousands of miles on old W123s and my experience has been that generally only one or two components need to be changed at once and that often there are problems with the (new) aftermarket parts not meeting the quality specs of the OEM German parts. If you replace everything and then have problems, you will need to be a front end genius to figure them out because you have no history of driving the car after meticulously changing one part at a time and observing the ride quality.

Just my $0.02.

Dkr.
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  #14  
Old 10-11-2020, 07:43 PM
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LOL it is mostly that spring which has me worried to be honest!

I'll be taking it to my local independent mechanic on Tuesday to have it lifted up and he agreed to give me a diagnosis, though I know for sure the lower control arm bearings are shot on the left hand driver's side and if their not the root of the problem, they are certainly not helping!

My thoughts are to be a bit conservative and let a shop take care of what I would consider more intermediate fixes requiring immediate attention (i.e. the lower control arms), and then taking care of the easier fixes on my own as I build confidence with components which aren't mission-critical. I'm going to buy the higher-end parts tonight for the bushings and the ball bearings.

Thanks for everyone's help and I'll let you what happens.
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  #15  
Old 10-11-2020, 07:44 PM
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LOL it is mostly that spring which has me worried to be honest!

I'll be taking it to my local independent mechanic on Tuesday to have it lifted up and he agreed to give me a diagnosis, though I know for sure the lower control arm bearings are shot on the left hand driver's side and if their not the root of the problem, they are certainly not helping!

My thoughts are to be a bit conservative and let a shop take care of what I would consider more intermediate fixes requiring immediate attention (i.e. the lower control arms), and then taking care of the easier fixes on my own as I build confidence with components which aren't mission-critical. I'm going to buy the higher-end parts tonight for the bushings and the ball bearings.

Thanks for everyone's help and I'll let you what happens.

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