300SD rear end sag

[gbrebes]

Hey guys,

I have a 1984 300SD that I have converted to run on vegetable oil. I have a two tank system with a 20 gallon oil tank mounted just in front of the diesel tank in the trunk. Because of this added weight in the trunk, the rear end understandably sags somewhat. I replaced the shocks a year ago when I bought the car. I got bilsteins, but not the heavy duty ones, damn. I was just wondering if there was some way that I could stiffen the springs or maybe get new stiffer springs to compensate this heavier load in the trunk. Also I searched this subject and read about the differential mount. How do you inspect one to determine if it is ready to be replaced?

Thanks for the help,

Gilbert

[my126benz]

U can purchase spring adjusters to wedge inbetween the rear springs. This should rasie the car up some. As much as i dont like pep boys i have only seen them there.

[Ara T.]

You probably have what, like 140, 150 extra pounds in the rear now? It shouldnt be sagging that badly, that's a lot less than your average American passenger... does it sag when people sit in the back?

[pawoSD]

I might try out some of those spring wedges too, if I can get rid of an inch of sag or so, mine will be great.

[gbrebes]

I think veg oil weighs around 7 pounds per gallon and I made my tank out of 14 gauge steel, so its pretty heavy-maybe 40 to 60 pounds. That puts it at almost 200 pounds full. My back seat is filled with two child car seats, so I have never really been able to check if the car sags with two full sized adults in the back. All I know is, when the tank is near empty it sags less than when it is full. I haven't bottomed out on anything, so its not really an emergency, I just thought it would be nice to raise the clearance a little.

Thanks,

Gilbert

[SirNik84]

i have the same car, 84 300SD, and it sags sometimes. i think my problem is the shocks, because they are factory original. i pulled one out and went to the parts house to find a replacement and they wanted to order me some for $200. but i wanted something a little stiffer to get rid of that sag. so i made an autocad drawing and gave it to a friend of mine whos family owns a 4x4 lift shop. finding odd shocks is his job. so if he can get me a stiffer and taller shock for less then $200 i'm gonna grab it. i'll be sure to post the serial number on here if he can find the shocks.

[kmaysob]

please dont use spring wedges. my first 300sd had them in the springs and when i bought it they had caused the shock to bust trough the trailing arm on one side.

[SD Blue]

I agree, avoid the spring wedges. Most of them won't even fit in MB springs.

Mine sagged quite a bit originally. Here are the areas that contributed:

Differential mount- usually very noticable as rise/squat when initially placing in reverse/drive. Visible inspection is very difficult to determine condition except for a "shiny" spot on the inside of the bottom of the vee.
Subframe Bushings- on mine, these showed up as rear tire wear and rise/squat.
Sway bar bushings, front and rear- slight change after replacement
Rear trailing arm bushings- caused an uneven height due to one being worn out
Spring pads- rubber, 350k+ miles, weight of car constantly on them, especially the rear ones can become oil soaked.

Unless you're discussing air shocks, shocks don't typically affect ride height. I wonder if MB made stiffer springs for the w126 chassis that saw a special use, such as Euro steel-sprung models that were factory equipped with a trailer hitch?

[Brian Carlton]

Here is a photo of two differential mounts.



The one on the left has 20 years of forcing down on the rubber.

The one on the right is brand new. See the space at the top (the bottom on the vehicle).

I had great success in ordering and installing a pair of coil springs from Coil Spring Specialties, Kansas.

You can read all about it in this thread:

rear suspension ride height