I had someone in the back seat and had a passenger say it rode like a pickup truck in the rear. Whatever that means, I take it was rough. There's new shocks all the way around. The rear end also floats everywhere at 70+

Where should I start looking? I am trying to take care of one thing at a time as you can see my signature is a full stable.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Bushings.

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CENSORED due to not family friendly words

Sedan or wagon? If wagon, I'd say the SLS system needs new nitrogen sphere accumulators. If sedan, I'd say the new shocks are wrong, should be Bilstein Comfort vs. Bilstein HD (heavy duty).

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Probably best to lift the car up and check for any bushings that are cracked or worse, smashed into oblivion. A couple of my bushings in my front suspension look like rubber pancakes and I'm getting ready to replace them soon.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Maybe they’re used to ‘50s boulevard cruisers. Take a ride in the back and decide whether the ride is harsh. I’ve been in some d@mn comfy trucks.

Sixto
98 E320s sedan and wagon

The rear subframe is suspended on 4 bushings, the front of those actually move whenever the arms move up and down and whenever the wheels torque to move the car fore and aft.

There is a remarkable difference in ride quality once those are replaced. The other factor is the little bushings in all the link arms, they need to be nice n solid and only tightened to spec at ready to drive level as they literally bounce the hub back to normal level when tested without the spring attached.

On my old W124 - I refreshed the entire rear subframe. The feeling of the car with new fresh rubber in the back is downright amazing. You will then understand why this car was so famous for its ride quality. (its firm yet supple) - it was never meant to float like a buick, think more of like a toyota supra ride quality

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)