Now that the spring is near, I'm thinking of starting few of those projects on the car that have been accumulating. One of them are the upper control arms (left and right) which have been squeeking like the devil. The left one in particular has a torn rubber boot around the ball joint, leaking grease.

I figured, I'll bite the bullet and just plan on replacing the whole assembly along with the rubber grommets, etc. hoping to eliminate those squeeks when I go over over bumps...

If one is fairly mechanically inclined, is this an easy/difficult job to do?! Looking under there it makes me think that I may need to deal with compressing the spring?! Is there a DYI on that topic? Any pointers would be appreciated.

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

OR "Advanced Search" function

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'84 300SD sold
124.128

this is definitely DIY... with the right tools. Your biggest challenge is removing the balljoint end of the UCA from the spindle arm.

Search for BGKast 's thread on the front end rebuild and ask him.

the rest is plug and play


I might mention that the squeaking is not from the UCA (perhaps) ?

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You can use a pickle fork in removing the old ball joint IF you get a new assembly, as it has a new ball joint already installed. Might as well, as the price difference is very little.
Support the vehicle on the lower control arm. No need to remove the spring.
There should be plenty of info using the search function. If not, PM me.

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83 SD

84 CD

ditto, thanks for clarifying

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Squeaking sounds like a lower ball joint. Replacing the lower one requires spring compression. But the upper control arm isnt too bad of a job at all. Here are some steps that are better if followed in order, being that the car is supported with jack positioned under lower control arm.

1. Release UCA from Spindle arm using pickle fork.

2. Remove bolt from wheel well mount.

3. Remove sway bar bolt.

4. Tilt UCA with ball joint end downwards, swiveling on sway bar.

5. Then slide UCA off of sway bar and remove all the bushings.

6. Check sway bar end for serious rust issues.

If all is well, the process is reversed.

I suppose that depends on how one defines "spring compression." A "spring compressor" is absolutely not required on a W123.

What price difference?

It's been a few years, but I looked it up just now, a new complete UCA is $47, just what I paid. {Firestone quoted me over $250 for the same part} So it's okay to destroy the ball joint removing it. Did NOT find just an upper ball joint.

To replace a lower (supporting) ball joint you do not need to compress the spring, as tf007 mentions. A mechanic did one for me in car, [squeaking horribly!] the FSM mentions to remove the spindle, requiring re-loading the outer bearing. And if you're going to do THAT, you might as well install new rotors, IMO.

To replace the LCA/bushing, you do need to compress the spring.

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83 SD

84 CD

Where do I get this pickle fork tool?!

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

Jack the front end up until both front wheels clear the ground, this helps unload the sway bar and makes reassembly much easier.

I also found a 2X4 (about 20 inches?) long placed on end on a floor jack placed under the sway bar during reassembly lets you move it up/down alot easier when trying to get the upper bushings to go back together.

Also many times a good couple of smacks with a small sledge will pop the ball joint easier then the pickle fork.

Dieselgiant has a writeup on replacing the UCAs. I did mine last weekend and the one thing to remember is definitely jack up BOTH front wheels, as DGuy says. The job was nearly (if not totally) impossible with the sway bar under load. I couldn't see a way to get the main holding bolt off the passenger's side without removing the battery tray, but maybe there was a trick that I missed. Also, I didn't see a way to remove the sway bar bolt without taking out the shock. DON'T DO IT! If your jack gives way from under the LCA, the whole assembly will shoot to the ground under the load of the spring. That will, at best, just break your brake wear sensor wire like it did mine. You can remove this bolt by just prying up on the sway bar with the shocks in place. I didn't have a problem removing the ball joint from the spindle. I was able to just give it a few smacks from below with a hammer and it freed itself up. All in all, it's definitely a DIY job.

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1981 300CD 260k w 60k on new motor
1983 240D 4spd Manual

Is there a diagram that would illustrate the differnet parts of the suspenion (sway bars, control arms, bushings, etc) - I have a FSM but it doesnt have a diagram of the suspension parts... Any help would be appreciated here.

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

I stand corrected as far as being able to replace the lower ball joint without a spring compressor. Tangofox07 did state however, that spring compression is not required for a W123, that is also incorrect. A person could not replace LCA bushings without spring compression. I own spring compressors, and even though you can do a lower ball joint without spring compression, I do anyways. To be safe I guess, I hate to think about my jack slipping, a spring flys out, breaks my jaw, and mangles my face for life. I just play it safe I guess.

Look up my post
Easy upper control arm re & re
A how to with pictures

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1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom