Changing out rear springs on 85 300D--Neccessary?
 

My 85 300D restoration is going smoothly. I was wondering about changing out the rear springs on the 85 300D. Perhaps to my imagination only the rear of the car looks low. There is nothing more unsightly than a sagging older car.
I asked my Indy and he said "Are you kidding? The only person he changed out the rear springs for a contractor who was hauling 700 pounds of bracks in his car everyday.
I still think my springs sag, though probably the car was never heavily loaded. The engine and tranny and rear are from a 200K mile car, but the springs have 330 K on them.
What should I do?

My experience, such as it is, is that the springs usually don't sag. When I've encountered problems with height, it has been fixed by renewing rubber components. On my 126 especially, replacing the subframe bushing made a big difference in handling and ride height.

Why do you suspect the springs? And just how much sagging are we talking about here?

Pretty much every 123's rear springs will be worn out by now. I compensated on mine by bringing the front down to match so its not 'nose high' anymore.

I should go home and measure it
 

Why do you suspect the springs? And just how much sagging are we talking about here?

I should go home and measure it. Thanks for the advice about rubber bushings.

yes the sub frame is the first place to look....that also is a key link to your rear alignment....then the spring cups for sag....but all in all its 20 years old...

not as a plug - but if you want new springs i have a set brand new that i could sell to you - they are sitting in my shop gathering dust....bought them when i lowered mine, ended up using the lowering springs with thicker cups....

good luck
Jake

Subframe bushings and rear differential mount would be the first things to check. On my W126, changing these helped significantly. I am not completely sure why but changing the front sway bar bushings also helped. I guess it lowered the front.

Cheap and easy way out
 

Just get some coil spring helpers. They're basically wedges that screw in between the coils to get back some of their original height. If your local parts chain doesn't carry them try ebay or JC Whitney.

Doing the rear mounts, diff and sub mounts, made a big difference. As said in the above posting, renew all the bushings in the upper control arm ( replace it if need be ) and that ought to really straighten the car up.

I noticed that biggest change after I replaced my upper control arm and all 4 bushings on it.

A brand new set of Bilsteins will add a 1/2" to the ride height. If you don't believe me try compressing one off the car. There is perhaps a 50lb upward lift per shock.

I have new Bilsteins front and rear already--
 

....but I guess reading what everyone is saying a rear end rebuild is needed...only makes sense, my front end is like a new car, new struts, bushings, tie rods, engine mounts, driver side spring switched with passenger side spring and vice versa, new rubber, everything done in 2004/2003.
However most of the parts on my rear end were already old during the Dark Ages.

Carrameow-

I did what you are talking about on my 240D-

Totally rebuilt the front and rear ends. New springs all 'round, new Bilsteins, ball joints, upper arms, bushings, rear subframe mounts. Still sits too low in the rear. Or is it that the front is way too high? I got the springs from Worldpac and eventually returned the fronts. The only thing I can think of doing now is adding shims to the back - and I didn't change the diff mount, but I can't see that being it by itself. :confused:

Richard,

You may not have read the complete story on the rear springs for the SDL.

It may give you some insight into the issues with the W123.

http://www.peachparts.com/shopforum/showthread.php?t=124073&highlight=springs

looks high
 

both the 123 and the 126 in my opinion are designed to look a little high in the front. this is accentuated by the fact that most of the newer cars now sit so low in front.

If your rear sags replace the usual suspect bushings. On a W126 it would be trailing arm mounts, and the diff mount. Off the top of my head I don't think any other bushing would cause the rear of a W126 to sag. If your shocks are old swap those out as well.

If the rear is still saging replace the springs.

Correction Hattie:

It's the subframe bushings and the diff mount. The trailing arm bushings won't affect the ride height unless they are falling out of the subframe. :eek: