Upgrading w123 rear trailing arms to aluminum w126 ones possible??? - PeachParts Mercedes-Benz Forum

nsantolick · #1 03-04-2009, 09:13 PM

Hi there;

I have a 1983 300D Turbodiesel and it has the normal, "rusted out rear trailing arms" issue.

I ordered a set of replacement ones from a West Coast Benz scrapper and received the package recently.

It turns out that they sent a part that is different than what my car has, but they insist that it's interchangable.

The best of my research leads me to believe that it seems to be.

Can someone please confirm this? The part that they sent me is marked with the numbers 126 352 04 04.

I looked that number up and don't find much. There is a set on eBay now, and they identify it as being off of an w107 car.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=380074381472&fromMakeTrack=true

I compared the two, and see that the new one is aluminum, which would be great as it won't rust out, and this car is definitely a keeper for me.

I get the feeling that some w126's used steel ones and others used aluminum parts, but just can't confirm.

ANYTHING to help clarify things for me would be most appreciated.

I'm getting a local shop to do this work and can't afford to be rear-wheel-less for too long with them so I really need to confirm that this is possible.

I noticed that the brake calipers seem to mount 180 degrees off from where they do with the parts I have installed. Aside from that though, I don't see why it wouldn't work.

Of course, if it would work, I'd expect to be able to find others talking about this upgrade.

Anyway - fingers crossed. Thanks for any help in advance...

nsantolick

1983 Mercedes 300D Turbodiesel
1971 Mercedes 280S

DeliveryValve · #2 03-04-2009, 10:24 PM

I recall reading somewhere that they were that same. But don't have that link.

But according to ADSITCO (my favorite parts store... Yeah right!

..... But I am sure their info is correct) the "Lower Control Arm- Rear" have the same part number.

W123

W126

And if you do a search on the Fastlane site, the trailing arms are the same part number.

So my guess it will fit and the Aluminum part is a nice discovery replacement for the rust belt folks.

charmalu · #3 03-04-2009, 11:56 PM

The only aluminium trailing arm I have see when crawling under PNP cars, looking for a few treasures. Is a W126 SEC. they do look different than the W123 as I remember. but who knows?

Here is a thread with some charts with what crosses over to what.

www.peachparts.com/shopforum/showthread.php?t=229825

Charlie

bgkast · #4 03-05-2009, 12:05 AM

I think you may have found a nice upgrade...

t walgamuth · #5 03-05-2009, 06:00 AM

I had an sec and always assumed they are interchangible. I don't know for sure, but I would take the yards word for it. A nice upgrade, IMHO, too.

Simpler=Better · #6 03-05-2009, 10:23 AM

No rust and less weight flying around-good deal!

JimFreeh · #7 03-05-2009, 07:36 PM

The cast units are found on the 500SE/L and the 560SEL.
And maybe on the equivalent SECs...

And.... are they not magnesium?

Jim

Graminal95 · #8 03-05-2009, 08:38 PM

Looking at the factory manual, it looks like the AL arms were an option for the w123 and w126. They have an anti-squat function too. I was thinking about this a few month back while I was under a 450slc, it would be a nice upgrade.

Oracle12345 · #9 03-05-2009, 08:50 PM

I would look up the specs for both but they cant be the same seeing that W126 is a much wider car than a W123.

bgkast · #10 03-05-2009, 09:02 PM

Quote:

Originally Posted by Oracle12345

...they cant be the same seeing that W126 is a much wider car than a W123.

...and so are the mouting points on the rear subframe

pawoSD · #11 03-05-2009, 11:11 PM

Aluminum! Wow....that'd be perfect for here in MI.....I'll have to let my dad know! (his are kinda rusty...)

t walgamuth · #12 03-06-2009, 06:08 AM

Actually the Rear track on the 126 is only slightly wider and is accounted for in the wheels. All parts, IIRC, are interchangible with the 123. The front on the 126 is about 2" wider and I believe most parts there are interchanbilbe with the 123 as well, they are just pushed apart to accomodate the v8s.

I was not aware of the antisquat feathure and am wondering how that might work considering the parts are interchangible and use all the same pivot points?

nsantolick · #13 03-07-2009, 12:15 AM

I'm excited to hear that it should work. I've asked around all over, and this forum had by far the most responses. There is only one person, on another board, who said it can't be done, and said that there a small differences between the aluminum arms and the original steel ones.

I'm not sure if they actually tried it, but they are a bit of an authority so it still makes me wonder. Nevertheless, EVERYONE ELSE seems convinced that it should work, so I'm hopeful...

There is no doubt though, that the brake calipers do mount 180 degrees opposite of where they did with the original arm. I'm not certain how much of a problem, if any, that this presents, but that is one significant difference that is obvious to me, when comparing the parts.

I hope that this will work. I really like the idea of the "upgrade" a lot now. I'll document things as much as possible for the benefit of all if we go ahead and try them, which I expect to see early next week.

Thanks soooooooooooo much to everyone for the assistance. I can't wait to get this car back on the road.

It's been mentioned that the aluminum arms were an option on w123's and w126's. Was this something that the customer could specify or moreso something that Mercedes would select, on their own, for certain cars/markets? I'm curious about that actually...

Thanks so much. All the best... : )

Nick - Hazleton, Pennsylvania
1983 300D Turbodiesel (black/black)
1971 280S (white/black)

nsantolick · #14 03-07-2009, 01:12 AM

This is what the only nay-sayer out of all the people that were kind enough to help me out here had to say. I just am curious if anyone here agrees...

"Even though they look the same there are enough small differences in dimensions and fit to make not doable."

I'm pretty certain now that we're going to at least try to fit these aluminum ones. Maybe further mods would be needed, but it seems so dam similar when examined closely, AND, everyone seems to concur that they should be interchangeable, and a nice upgrade for rust-belt area w123'ers... : )

t walgamuth · #15 03-07-2009, 06:09 AM

I suggest installing new brake lines if the location of the calipers is different. They will have taken a set where they are and will probably crack and leak when you rearrange their location.

I found this when I upgraded my 115 to 123 front calipers.

It took a month or so but they began to seep.