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  #16  
Old 03-05-2013, 04:12 PM
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I'm going to second Brian Carlton here by saying that maximum difference in rear height on a 126 car is going to be from springs, and to a limited extent, shocks, if they have gone bad. I never see much of a difference from new subframe mounts. Hadn't considered the role of the diff mount, and I'd like to explore/hear more about it's and the subframe mounts' role in proper rear end alignment. But don't forget the metal tube in the center of the subframe mount. It is going to put a hard limit on the amount of collapse that can occur, and when you install new mounts and torque down the 24mm bolt through the center, it collapses them anyway!

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  #17  
Old 03-05-2013, 04:31 PM
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I don't recall a 24mm bolt anywhere in the 126. Nothing even close in our 3/4-ton Suburban.

Yes, I know what you meant

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  #18  
Old 03-05-2013, 04:53 PM
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Quote:
Originally Posted by Brian Carlton View Post
While it would be desirable to recover that 3/4", most vehicles won't benefit by more than 3/8" when the subframe bushings are replaced. My previous experience with the SDL shows that you can spend your money elsewhere (spring pads, differential mount, shocks) for more gain.

Installing new Bilstein shocks gave the SD an additional 1/2" just from the proper gas pressure.
True. The main benefit of replacing worn subframe bushings is to minimize rear axle disagreement with the steering wheel.

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  #19  
Old 03-05-2013, 06:57 PM
macdoe
 
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Quote:
Originally Posted by qpooqpoo View Post
To eliminate rear end sag you must change your Differential Mount AND Subframe Bushings (the two very large round ones).

This is going to sound snooty but forgive me:

The w126 subframe architecture is such that the diff mount and subframe bushings work IN CONJUNCTION with eachother to create a positive-camber platform. If any of those 3 rubber bits weakens or fails, the leveraging effect of the system fails, you lose camber, undue force is put on the springs, and the car saggs.

Also, asymetrical rear end sagging is almost always due to asymetry within the system (i.e. One subframe bushing is bad)

Only after this subframe system fails does excessive pressure begin to be placed on the shocks and springs, leading to their loss of strength, thus exaserbating the sagging further.
According to this....if one of the subframe bushings is bad and the other fine, then even if you were to fix the diff mount and put new springs and shocks and correct rubber shims to correct the sag. The fact would still remain that one subframe bushing is bad...therefore the alignment and sag would still be uneven if all other things to remedy the sag were fixed due to you starting out with one side at a different starting height (bad s/f bushing side) than the other.

It would appear that the subframe and diff mount locations would be an important starting point for correct and equal ride height for alignment purposes and the springs and rubber spring pads more to correct the ride height itself. Both are relative to each other and the deterioration of the subframe mounts and diff would perpetuate wear on other springs and shocks and rubber bushings in the rest of the rear suspension system, especially if one side was worn more than the other. Would this be considered like a three link suspension system then?

Last edited by macdoe; 03-05-2013 at 11:26 PM.
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  #20  
Old 03-05-2013, 06:59 PM
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ok so i have not done any of this yet. i have my HD bilstein shocks in the cart. Daniel at PP recommends replacing the springs as well at 300$+. what about rubber parts that need to be replaced. also i am curious about a slight vibration in the rear with some weight in the trunk. how often are the bearings redone?
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  #21  
Old 03-05-2013, 07:22 PM
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Quote:
Originally Posted by oldtown View Post
Daniel at PP recommends replacing the springs as well at 300$+.
............no surprise there..........
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  #22  
Old 03-05-2013, 11:19 PM
macdoe
 
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Quote:
Originally Posted by oldtown View Post
ok so i have not done any of this yet. i have my HD bilstein shocks in the cart. Daniel at PP recommends replacing the springs as well at 300$+. what about rubber parts that need to be replaced. also i am curious about a slight vibration in the rear with some weight in the trunk. how often are the bearings redone?
Quote:
Originally Posted by oldtown View Post
I have had it with the rear end sag and i am currently pricing parts. my question is what should i replace as far as rubber bits. Also what combination do i do.
i was thinking for the rear, HD Springs and shocks and just regular bilstein shocks for the front and not messing with the springs up front.

any suggestions and what others have done? success? failures?
How about this....

Quote:
Originally Posted by foolio View Post
To "lift" my rear end on my 420SEL, I replaced:

Springs - stock OE
Spring pads - stock (can't remember which nub off the top of my head) OE
Subframe bushings - stock OE
Trailing arm bushings - stock OE
Diff mount - stock OE
Shocks - Bilstien Comfort

By doing this, I gained just under 2" of ride height in the rear.

The rubber parts in this list are the spring pads, subframe bushings, trailing arm bushings, and diff mount.

There might also be the trans mount and driveshaft support and bearing to consider, if you have vibrations but that is hard to say from far away.
-could be vibration from suspension geometry being screwed from sagging and warn suspension related parts.
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  #23  
Old 03-05-2013, 11:31 PM
macdoe
 
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Quote:
Originally Posted by Brian Carlton View Post
I've spent quite a bit of time with the ride height of the W126. The approach that I took with the SD differed from the approach with the SDL.

To get the ride height back to perfection with the SDL required a set of new springs. However, after purchasing the stock springs, I find that the vehicle still sat low in the rear with any load whatsoever in fuel or in baggage. To get the proper height required some custom springs with an additional 5/8" length. The vehicle now sits a tad high in the rear with no weight. I might lower it slightly with thinner pads.

The SD was quite successful by using the stock springs. The diff mount was replaced and the spring pads were replaced to the maximum thickness three nub pads. The main success on the SD was accomplished by replacing the front spring pads with the very thinnest possible one nub pads. This cured the high front end look and simultaneously raised the rear slightly. The vehicle sits perfectly now...........just slightly high in the rear with no weight and dead level with full fuel and about 50 lb. in the trunk.

So, before you waste a bunch of money on springs, determine if a change of pads and the replacement of the diff mount will cure your problem.
Like Brian says at the bottom of this post...maybe you could do everything on the above list from foolio except the coil springs and see what happens....but on the other hand if you have the money to spend it would be easiest to do it all at once while its apart....like most things on these.

-pay special attention to Brian's use of the THREE NUB rubber spring pads...

Last edited by macdoe; 03-06-2013 at 12:07 AM.
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  #24  
Old 03-06-2013, 07:53 AM
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thanks folks , that is what i needed. i am going to get with daniel to see what sort of deal he can make me. also i think i am having starter troubles. is the starter servicable?
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  #25  
Old 03-06-2013, 10:06 AM
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I am trying to get my head around the geometry of the rear subfram on the sd. Would placing a plate as a shim between the diff mount and the body make the rear end sag better or worse? I too am dealing with sag but have other things to deal with as a priority. Just looking to cure the symptom for now and deal with the cause later.
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  #26  
Old 03-06-2013, 10:10 AM
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Quote:
Originally Posted by weird beard View Post
Just looking to cure the symptom for now and deal with the cause later.
If finding the issue is of no concern to you and, obviously fixing it correctly isn't a priority, just go and purchase those "spring helpers" which prevent the coils from fully compressing. You can see them in post #13 on this thread.

Fast and cheap and totally improper, but...........it'll probably work for you.
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  #27  
Old 03-06-2013, 11:52 AM
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FYI

Quote:
Originally Posted by sixto View Post
I don't recall a 24mm bolt anywhere in the 126. Nothing even close in our 3/4-ton Suburban.

Yes, I know what you meant

Sixto
87 300D
Step# 9 sub frame bolts are 24 MM.
PeachPartsWiki: Replacing the Rear Shocks & Springs


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  #28  
Old 03-06-2013, 01:08 PM
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FYI

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Originally Posted by whunter View Post
Step# 9 sub frame bolts are 24 MM.
PeachPartsWiki: Replacing the Rear Shocks & Springs


.
The size of the wrench utilized to turn the fastener is not the size of the fastener.

Those bolts are not 24mm. If they take a 24mm socket, they are M16.
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  #29  
Old 04-05-2013, 05:40 PM
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all done . after new shocks and springs and new seat pads and seat spring repair the 300SD is a new car. i am glad i went with the comfort shocks and springs, it is truly an awesome ride.
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  #30  
Old 04-05-2013, 07:05 PM
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Quote:
Originally Posted by Brian Carlton View Post
The size of the wrench utilized to turn the fastener is not the size of the fastener.

Those bolts are not 24mm. If they take a 24mm socket, they are M16.
aww, give Roy a break, he's going through a lot right now...

just IMAGINE a 24mm bolt being used on this car! THAT'D create some sag!!!

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