Trying to fit an aluminium W126 / 107 trailing arm to a W123 - a question of compatib
 

Dear All,

I've stumbled upon some reasonably priced W126 aluminum trailing arms that I would like to fit to my W123 300D... I read on this forum that it is possible to fit them but:-

Has anyone here actually done the job?

Has anyone here got W126 aluminum trailing arms on their W123?

I've found this thread but it seems as though the poster was being messed about by people. The verdict is that it can't be done:-

http://www.peachparts.com/shopforum/diesel-discussion/246721-upgrading-w123-rear-trailing-arms-aluminum-w126-ones-possible.html

I'm not satisfied by this just yet (sorry!)

The seller does say that I need a different shaped anti-roll / anti-sway bar. This to my mind does indicate some different geometry if that is the case.

As usual any help will be greatly appreciated - particularly from those who have done the job.

A desperate Sunday evening (well afternoon where most of you are) bump!

I'm not getting a warm wet feeling about this one... perhaps it isn't possible after all?

At the rear, outboard end of the swingarm there is a design difference described as "anti-squat", it can be found described in the 126 Body and Chassis FSM. I suspect that is the fundemental basic difference between the standard swing arm and the aluminum versions found on 126 coupes. How does this difference manifest itself as far as what will fit and what limitations on parts that connect are not known to me other than the differences exist. Good luck!

Yet again - thanks for your help Billybob - a good shove in the right direction. The seller won't ship the parts so as I've got to go and see them, I'll take a W123 trailing arm for comparison, a camera, and a tape measure. And in the meantime I'll leaf through the FSM. Cheers!

Update - finding information
 

Hmmm I thought I'd find more information on this. It seems to be common knowledge that the steel trailing arms are interchangeable... but I can't find much information about the aluminum versions.

I've read through chapter 35 in the W126 FSM and I can't make out for sure if the trailing arms with the anti-squat geometry were aluminum or not - I guess so...

It looks like I'll have to see these parts in the flesh.

To be continued...

Did you try looking at part numbers in the EPC?

Nope - I don't have it - I'll have a chat with the friendly dealer and see if he can help out.

My memory is foggy....
 

..... but I recall looking into this....

I recall the cast arms were titanium, and were issued on the 500 and 560 models. Diesels and smaller engined cars had the stamped steel like the W123. My 85 500SEL euro car had these cast arms, so I don't think they are exclusive to the 86 and up redesign.

From what I could see, it appeared the cast arms (forged?) were interchangeable with the stamped steel.

I also recall this may involve a change in the way the disk caliper mounts, but it certainly looked like the cast W126 arms would xfer to the W123, if the different parts were also changed over.

Jim

Thanks for your input Jim. I got that impression from the FSM as well - but I need to check out the geometry of the trailing arm to make sure all of the (redundant) anti-squat stuff isn't necessary. I'm also a bit concerned about dissimilar metal corrosion... so I'll have to look into that too. (Clarification:- bunging the old W123 steel bits onto the luxurious alloy casting may not be so smart - I don't know - I'll have to see).

http://viewer.zoho.com/docs/rackve

Cross Reference List, 300d as source for pn

Hope this is useful

Wow thank you very much

1263503205 seems to be the steel one according to http://www.german-spob.de/start.php?seite=gebrauchtteile&seite_gebr=suchergebnis&suche=&language=eng

I'm not sure of the material used however, I do know that theres a right side and left side. I used those are the basis of my parts search.

• http://i.imgur.com/ghKUcl.jpg

Oh great - this is a great help - this more or less confirms that the alloy (well non steel - whether it is aluminum or titanium remains to be seen) is with the anti-squat gubbins.

I've found these pictures in the FSM:-

http://www.peachparts.com/shopforum/...1&d=1291824355
http://www.peachparts.com/shopforum/...1&d=1291824363

You can see there are extra bits by the hubs

Well it has been a long time...
 

...since I've thought about this but this picture prompted me to think again

http://www.peachparts.com/shopforum/...1&d=1318352907

This is actually a second generation W126 sub frame and trailing arm assembly... but it got be scuttling off to the Russian EPC site (EverythingBenz - Mercedes-Benz Forum and Web Search Using Google) to have a look at those lovely aluminum trailing arms.

Here's the first generation W126 sub frame

http://www.peachparts.com/shopforum/...1&d=1318352907

And these are the aluminum trailing arms

http://www.peachparts.com/shopforum/...1&d=1318352907

Part 116 must be a big bit of the anti-dive mechanism. There must be a big bit that goes across the back of the car there...

I said ages ago I'd go and make some measurements - I never did... but I might have the chance to see some real ones soon. Stay tuned!

And here's the rear anti-roll bar
 

It looks very similar to the W123 set up...

http://www.peachparts.com/shopforum/...1&d=1318357726