W115 and W123 rear suspension interchangeability
 

I'm a vintage diesel Mercedes addict, it's official.

Last night I just closed a deal and made an agreement to buy a 1972 220D that has been mostly garaged in a much drier climate than where my 1978 300D came from (some moist pine forest in North Carolina.) Now that I know what to look for and where to look, I feel like I got a gem in this 220D.

That said, last year I replaced all the bushings in the rear of my 1978 Benz and a lot in the front. My question is, will all the parts between the W123 fit into the W115? Yeah, you know what I'm thinking. It would be a lot easier to just move the whole rear end (without the differential) from the later chassis to the earlier one. I'm not looking forward to replacing those bushings but since this car has less rust (only 2 small spots) it might be easier anyway.

So, does anyone know the answer to this? The subframe and trailing arms look very similar but even a tiny bit of structural change would make them incompatible.

Thanks all!

Phil Forrest

No input on this?

Phil Forrest

I could be wrong but I was under the impression that the 114/115 and 123 suspensions were completely different designs. Ie, nothing will interchange.

- Peter.

From underneath they look identical.

Phil Forrest

You might have something. '76 115 and '77 123 use the same trailing arm and differential bushings but different rear subframe bushings. 123 trailing arms might have provisions for SLS even if SLS wasn't offered on US sedans and coupes so they will be different but maybe MB only added bosses and attachment points. You'll need to visit the EPC to be sure.

Sixto
87 300D

I ask for two reasons:
First is in my original post.
Second is because a friend and fellow forum member has a 220D with a very bad case of what is "negative camber" I guess. The wheels point inward at the ground side. Tires wear out quickly and handling could be better. I'm wondering what would also cause this.

Phil Forrest

I am under the impression the rear suspensions are very very similar if not identical. Are you planning to swap the diffs too? They are different in gearing.

My vote is that the trailing arm assemblies are the same - as far as I am aware there is only a difference in a part that is fitted to the W116 version (of the same arm) that allows (some of the) larger diameter homokinetic axles to be fitted. In short I'm (kinda like) 95% positive the W114 / 115 / 123 / 126 first generation all have the same trailing arm. W116 is in there too but some of the models have a larger diameter axle (source for that nugget => W123 FSM - chapter for rebuilding axles).

A quick check on EPC is confirm / deny this <= I still haven't bought it here so I can't check for you.

The sub frame, however, I am less certain about.

Positive camber => wheels further inboard at the bottom <= indicates too high a ride height. Check for the correct springs / shims. Sounds like it could have been modified (perhaps for towing?)

I'm pretty sure the arms are compatible. I generated this chart for a 126 and the 115 and 123s were both compatible with the 126..so I would assume they are also compatible with each other.

http://i.imgur.com/GFloIQW.png

Thanks for the correction.

The car with the camber problem is set up with a greasecar kit but the rear end is still low I think. Could just be a matter of changing those spring spacers then.

As for my 220D and 300D, I'm not sure. I'm going to have to get out the calipers and take some measurements as well as ensure angles are the same if I swap the rear suspension. It sure would be easier than redoing all those dang bushings. That was a chore. Now I know how to do it though so it wouldn't be as bad but still, it would be a pain since I don't have access to a lift.

To answer a previous question, each car would keep its respective differential, only the suspension would be changed.

I'm debating how much work to do anyway. The "new" 220D feels pretty tight on the road. My 300D was noticeably sloppy due to bad bushings but this one has supposedly been garaged for years in California. That's not to say bushings may not be rotten in the 220D but it hasn't been a daily driver around North Carolina which is where my 300D came from. It needs new shocks front and rear for sure. But I learned last time I did that to replace the bushings at the same time (if they need it) since the rear end suspension is going to be dropped anyway.

Phil Forrest

I am of the opinion as well that the rear suspensions are identical. I threw a differential from an 83 300D and axles from the same car into my 115 without incident. It was actually much easier to do because of the pop out plastic covers in the trunk on the 115, giving you above access to the diff nuts. What a great idea.

On the front, the suspension is completely different, BUT, I actually think it looks more modern personally.

Sorry... which is more modern? The W123 or the W115?

the W115 is an older design for MB, but its a basic double wishbone suspension thats still in use on a lot of brand new cars. It just feels more modern to me driving my 74 240 (back in the distant past when it drove) vs driving my 83 240.

If you look under a 115 and look under a 2010 honda accord, you will see physically different, but principally the same concept double wishbone suspension designs.

Mercedes seems to have re-visited the idea of wish bone suspension since the W123 - W201 and onwards seem to be single wish bone designs. I guess double wish bone is just too expensive (even for MB - though apparently not for Honda!)

Oh sorry I misunderstood then. If the rear end is too low then that's usually due to dead rubber parts on the subframe and the differential mount.