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

Stretch · #1 12-04-2010, 01:45 PM

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/showthread.php?t=246721

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.

Stretch · #2 12-05-2010, 01:49 PM

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?

Billybob · #3 12-05-2010, 02:27 PM

Quote:

Originally Posted by Army

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!

Stretch · #4 12-05-2010, 02:31 PM

Quote:

Originally Posted by Billybob

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!

Stretch · #5 12-06-2010, 03:13 PM

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...

rs899 · #6 12-07-2010, 01:00 PM

Did you try looking at part numbers in the EPC?

JamesDean · #7 12-08-2010, 09:01 AM

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

Cross Reference List, 300d as source for pn

Hope this is useful

Stretch · #8 12-08-2010, 09:36 AM

Quote:

Originally Posted by JamesDean

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

JamesDean · #9 12-08-2010, 11:01 AM

Quote:

Originally Posted by Army

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.

Stretch · #10 12-08-2010, 11:06 AM

Quote:

Originally Posted by JamesDean

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.

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:-

You can see there are extra bits by the hubs

Stretch · #11 10-11-2011, 01:14 PM

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

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

And these are the aluminum trailing arms

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!

Stretch · #12 10-17-2011, 08:33 AM

Here's a start of the week bump (now it has been rehoused to DD - thanks mbdoc!)

t walgamuth · #13 10-17-2011, 08:58 AM

It looks like if you use the compatible anti sway bar and the entire a arm plus hub assembley you will be good. My queston though is the mounting bolts for the aluminum assembly. The anti squat parts look like they will stress the sway bar with for and aft loads which the original standard steel parts would not do.

I am guessing there will be modification necessary there to make them work.

Stretch · #14 10-17-2011, 12:18 PM

Quote:

Originally Posted by t walgamuth

It looks like if you use the compatible anti sway bar and the entire a arm plus hub assembley you will be good. My queston though is the mounting bolts for the aluminum assembly. The anti squat parts look like they will stress the sway bar with for and aft loads which the original standard steel parts would not do.

I am guessing there will be modification necessary there to make them work.

Thanks for the input.

I don't know for sure but the anti-roll bar in the picture below (number 5)...

...looks very similar to a W123 one. It even has the kinks in the corners. Number 8 looks a bit different and beefier at the mounting points (that's the bit for the anti-squat variation).

According to wikipedia the width of the SEC was 1828mm instead of 1820mm for the other W126s - I guessing the extra 8mm was in wheel arch flares though!

Mercedes-Benz W126 - Wikipedia, the free encyclopedia

The W123 has a width of 1784mm

Mercedes-Benz W123 - Wikipedia, the free encyclopedia

So I think the anti-squat anti roll bar from a W126 would have to be cut / modified or perhaps the anti-squat fittings added to a W123 anti roll bar...

andydiesel · #15 12-09-2011, 07:33 PM

I'm planning on fiting the alloy arms to my 350sdl - have both steel and alloy arms in my workshop.
My guess is that the anti squat suspension is heavier than the standard one - despite the alloy arms.
Keep in mind any used parts will be at least 20 years old and will likely need rebuild. There are 5 bearings per side. A bearing supplier has quoted me $560 (CAD) for two radial bearings...you may want to change the linkage bushings - likely MB exclusive parts. There are some throwaway parts in the hub assembly...Emerg. brake cables appear different, ditto for the calipers which are mounted forward of the axle...

Tip for buying used: stay away if the steel sleeves sealing the joint connecting the arm to the hub yoke have rusted thru....The alloy will likely be pitted...also check for corrosion at the shock absorber mounting studs.
The brake shield and the emergency brake mounting base may be corroded beyond repair...