Replacing rear control arm - PeachParts Mercedes-Benz Forum

dac · #1 11-10-2015, 07:54 PM

I drive a 1984 300TD wagon, and it's been making some creaking/grinding noises every once in a while. I took it in today for a quick inspection, and got bad news. The rear control arm is rusting through with some holes/cracks. It needs to be replaced. One junkyard has one in stock for $250, and mechanics are quoting me around $900 for labor.

Long story short, I don't mind getting dirty and I can go without the car for a little while. Is this realistic as a DIY job? I may have access to a lift and may get some help from a friend. Do I need to pull the whole axle? I've heard the bushings can be very difficult to remove. Will I need a special tool?

Thanks in advance for any advice,
dac

Diesel911 · #2 11-10-2015, 09:16 PM

It is coverd in the Repair Links. Don't know if info about the SLS is there concerning removing the Control Arm.

Repair Links
Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

I did it on a regular W123 with no SLS on the Driver Side rear. On the right reat you man need to remove the Drive Shaft an Flex Disc because when you remove Arm Bolt near it it hits the disc.
Or maybe the Blot can be pulled out enough and left in place without pulling it all the way out?

I think you are also supposed to Torque the Arm Bushing Bolts with the weight of the vehicle on it and on the ground but I was not able to do that. Has a heafty torque.

Perhaps at that point you could put the Blocks under the Wheels so you have enough room to get under the Car.

I put on an used Control Arm but did not change the Bushings. It might be a good idea to do that.
Also the end play on the Wheel Hub ought to be checked to determing if the used Arm Wheel Hub Bearings are OK.
I did not do that because I had no car and had to get the Arms from a City far away by UPS.

t walgamuth · #3 11-10-2015, 09:56 PM

$900 seems very strong for one side especially.

dac · #4 11-11-2015, 12:37 AM

Thanks for the repair links. I forgot to mention that it's the driver's side rear control arm. I'm also curious if the SLS is going to make this a lot more complicated.

charmalu · #5 11-11-2015, 12:38 AM

Wow, that's a lot of money.

dac, do you have any PNP type junk yards in your area?
You can pull the parts off a W123 in the yard and learn how to remove everything.
I bought 2 Trailing Arms several yrs ago, think I paid around $45 ea, and that
included the Hubs backing Plate, Parking Brake assy and Parking Brake Cable. Of course, I pulled the parts.

The Trailing Arms from a W126 and the Differential is the same also, and will fit a W123.
That is the first Generation 81 - 86.

You will want to use the 123 brake cables as they are longer than the 126.

I don`t know how long you have had the wagon or how long you plan to keep it.
Do you just want to patch it up and sell it or keep it a long time. This will depend on the answers you get.

http://www.peachparts.com/shopforum/diesel-discussion/276507-rear-subframe-removal-bushing-replacement.html

http://www.peachparts.com/shopforum/diesel-discussion/266324-w123-1984-300td-wagon-rear-trailing-arm-bushings-r-r.html

http://www.peachparts.com/shopforum/diesel-discussion/300593-bottomed-out.html

If all else fails.

https://www.youtube.com/watch?v=lqsI3fl1Z8w

Charlie

sent from my pos computer

dac · #6 11-11-2015, 01:43 AM

Charlie,
I love my wagon and would like to hold on to it for a while, so I'm looking for a more permanent fix. I'm in San Diego and there are some good PNP yards around here, so thanks for the tip. What should I be looking for when looking at control arms? So any control arm from a W123 or W126 would work?

Thanks,
dac

dac · #7 11-11-2015, 03:11 AM

Also, are the rear trailing arm and the rear control arm the same thing?

charmalu · #8 11-11-2015, 03:26 AM

Try to find the lowest mileage arms, then you have a better chance of good rear wheel bearings.
Replacing rear bearings is a lot harder than the front one`s.

PeachPartsWiki: Replacing the Rear Wheel Bearings

This is one job I haven`t done....yet.
When I replaced the Trailing Arm Bushing and Sub Frame Bushings, I found a set
of arms and Diff. from a 85 300CD with a lot lower mileage than what our 85 300D had.

Being in SD you should find a lot of rust free cars in the yards.
If you come across any W126 with aluminum arms, they will not work on a W123.
I think it is some of the SEC`s (Coupes) and 560SEL.

This is what works best for ME when pulling Diff, Axles etc... I have done a bunch in the yards, and tried different ways.

The last few I did, I just dropped the whole Sub Frame assy. on the ground and dragged it out
then took it apart.

Remove the Shocks.
Remove the DL from the Diff., I leave the Disk on the Diff. and pry the DL off.
may have to loosen the 46mm nut and center support bolts so it will compress.
Remove the Sway Bar at the Links behind the wheels, then rotate it up out of the way.
Cut he brake hoses to the Calipers.
Remove the parking brake cable where the ends attach under the car.

If this is a w126, then just cut them off as they are too short for a w123.
I haven`t measured them, read that on another thread. Maybe measure your car then the 126.
They are a pita to R&R.

Remove the 4 13mm bolts that attach the Diff mount to the body.
The Diff will drop down a ways, don`t have your head in the way.
Place a couple tires under it just in case.

As the assy. tips down, the springs will fall out. they are not under much compression.
Don`t panic.

Remove the 2 17mm bolts on the plate where the SF mounts to the body
then the big center bolt. Don`t remember the size. then that side will drop down.
Do the same on the other side. Your assy should be on the ground.

I then drag it out from under the car
Remove the 13mm axle bolt in the center of the hub.
Then there is the 2 big bolts on the Trail Arms. Think they are 24mm.
Remove these and the arm will slide off.

If the axles are good, pop off the rear cover of the Diff, and remove the "C"
clip and pull the axle out.

Iam doing this from memory, so may have forgot a step. and.....
This works for me and Iam 71...so no complaining. LOL

Charlie

sent from my pos computer

t walgamuth · #9 11-11-2015, 05:51 AM

I've paid 2 to 300 labor in the past for one side.

vstech · #10 11-11-2015, 01:20 PM

Quote:

Originally Posted by dac

Also, are the rear trailing arm and the rear control arm the same thing?

yes.

vstech · #11 11-11-2015, 01:23 PM

New these trailing arms are over 3K... so, I have been hoarding them... especially when you consider how tremendously difficult changing the wheel bearings are...

I recommend finding one in good shape at a pickandpull and pulling the bushings, and replacing them... it's your call on the bearing... MASSIVE amount of trial and expensive error to replace them.

BWhitmore · #12 11-11-2015, 01:26 PM

Labor rates in Southern California average $125-$150 per hour. Northern California is even higher.

t walgamuth · #13 11-11-2015, 02:25 PM

Its 75 here, so I guess that translates to 400 to 500 per side. 900 seems pretty high still unless for both sides perhaps.

dac · #14 11-11-2015, 02:59 PM

So I spoke to another mechanic who took a look at it and quoted me $275. $100 for a used part and $175 for labor. He comes recommended as cheap and reliable, so I'm going with it. I'll let you all know how it turns out.

Graham · #15 11-11-2015, 05:20 PM

Quote:

Originally Posted by dac

So I spoke to another mechanic who took a look at it and quoted me $275. $100 for a used part and $175 for labor. He comes recommended as cheap and reliable, so I'm going with it. I'll let you all know how it turns out.

If I could find a deal like that around here, I would have both sides changed!

Checked driving distance to your mechanic - about 2500 miles, 39 hrs each way