... and the rear end of my car is sitting low too.

Its an 84 300sd. From ground to wheel well is 26 1/4 on the passenger rear and 25 on the driver side in the rear.
I was boning up on old threads in preperaton for a spring job but the more old threads I read the less sure I am of what to do. Shocks, springs, or subframe bushings.
I go under the car to peek around to investigate the subframe mounts and I dont see anything that looks like the picture of a subframe bushing on fastlane. Where do these things sit? Are they under the springs?

And perhaps a topic for another thread, the front suspension you must hold the wheel about 20degrees to the side to go straight and it will shudder in a gentle turn on the highway. Is this as simple as an alignment or is it more serious?

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I have some personal experience with your exact situation and have spent several months working the issues out of the sagging rear on the SDL.

The first thing that should be done, before any consideration is given to the springs, is the differential mount. This is the steel and rubber piece that bolts the subframe to the body. It doesn't actually hold the differential, but is located right behind the differential. Over 20 years, the rubber compresses and the ride height will drop by about 3/4".

The second thing that should be done are the subframe bushings, which sit between the body and the subframe. These are located at approximately the middle of the passenger door, very closed to the outside of the vehicle. If you go underneath, you can find them by looking for a single very large bolt. The bolt secures the subframe bushing to the body. You can't see the bushing because it has a sheet metal cover over the top of it. Two additional, smaller screws hold the cover to the body.

Personally, I don't believe the subframe bushings affect the ride height all that much, due to their location, however, after 20 years they get brittle and have cracked in a couple of places, so they are due to go.

After doing this work, then replacement of the springs can be considered, if the ride height is not up to par.

I wasnt even looking in the right neighborhood, I would never have seen it if it wasnt pointed out. Anyway. They seem still reasonably pliable and not like they are crushed out but the driver side (lower of the two sides) seems in worse condition than the other. When you reach around to the top there is some play in the smaller bushing over the top on both. Does this mean that the big bushing has crushed out this much?
I couldn't find the differential bushing on fastlane (is it also known by another name?). But this part couldn't account for my asymmetric sag could it?
Uncoupling this suspension stuff seems pretty scary. Do you jack the car up by the arm that goes to that subframe bushing?

Also any thoughts on were to start on the front end?

__________________
84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

Yes, you definitely need to change the subframe bushings, based upon your description of the problem.

Here is the differential mount:


http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1JU1236H41KT0TJCDY&year=1984&make=MB&model=300-SD-002&category=All&part=Differential+Mount


To work on the two subframe bushings and the differential mount, I would encourage you to get the vehicle up on suitable jackstands, located at the rear jackpoints. Understand that the springs are trying to drive the subframe downward, so, when you remove the large bolt from the subframe bushing, the subframe will drop, because it is supported on two of the three points. Do one subframe bushing at a time. Then, when you are ready to do the differential mount, support the bottom of the differential with a suitable jack, so the subframe doesn't hang by the two subframe bushings.

The front end requires a diagnosis based upon condition and symptoms. It's difficult to just take a stab at what it might need.

one side is a lot lower than the other that could make your car pull. also you might look carefully and make sure that nothing is bent back there. if the car was slid into a curb the big a frame might be bent.... dont ask how i know... yeah brian... another of my daughters, #2 this time, slid on ice and hit a curb left rear tire first.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Did it bend the subframe or just the trailing arm?

The subframe is a costly fix, I'll bet.

I had the same issues. I went ahead and replaced springs, shocks, differential mount and the sub frame bushings at the same time.

If I had to do over again, I would do shocks and differential mount first. I tried the BOGE shocks which is an OEM producer for Mercedes. I like them. They were a little less than Bilsteins. But if you can spring for the Bilsteins - get them.

My 22 year old sub frame bushings didnt look that bad. But the springs did make a big difference. I can take sharp curves at 70 MPH now and the car stays where it should in the lane. Before the repairs, the rear end would wander. It holds the road incredibly now, rides better and does not sag. I got over an inch of lift. However my pinion bearing in the rear end started making noise after this repair. I guess it had been riding in sagging position too long.

__________________
1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

ooooooh. It sounds too good to be true. Even if there is just a small chance that changing the subframe bushings could fix the pulling problem in the front that has got to be my first move.
It sounds pretty straight ahead like I could probably do these in an hour. Once the the bolt is removed the force will be downward at that area. So... Perhaps a jack on the arm to push upward to do the work. Right? or not even necessary?
Thanks so much to everyone for the help.

__________________
84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

Well, an hour is a bit optimistic.

After you remove the bolt, the subframe will drop about three inches. Then, you must fight with the bushing itself to remove it from the steel pocket that it resides. You don't have a good angle to work here, and you don't have the proper M/B tool to force the bushing out. So, it's going to fight you and take some time.

When you get the new bushing installed, you will need to jack up the subframe into position to get the bolt started.

The change of subframe bushings will not cure the pull on the front end.

just the arm.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Well, that's not too bad, provided you find a used one.

for cheap.

i also found one for my son after his rusted out. his wife came home from a trip and said that the wheel cover had fallen off and would i take a look at the car? a 83 240d. i walked out and the top of the wheel was in about 3". if it grabbed the wheel and pulled it would wiggle a lot. i still marvel that she made it home wo the arm totally collapsing.

oh yeah, about 10 years ago i had to replace one when the shock mount rusted away....too. if you drive the same models long enough it all begins to sound like de ja vu.

one of them i dont have to worry about... the sec has forged or cast aluminum a arms in the back. i have often wondered if they affect the geometry or are just to reduce unsprung weight.... any body know? that sec really hugs the road. the springs are firmer too.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

just a results follow up for anyone searching old threads. I replaced the rear subframe bushings. It is a really fast job execept that one of the bolts stripped. A 14mm 1.5 tap fixed that.
The result is 3/4 inch increased height on both sides of the car in the rear compared to my measurement just before putting it up on jackstands. too early to tell if the initial height will "settle in" after a little driving.
According to senior member brian 85ft lbs is the torque amount for how much to tighten the big bolt.

__________________
84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.

Good job.

Now, replace that differential mount. If it's original, it also should be done at the same time. Over time, there is a section of rubber that gets compressed and allows the body to settle.