I OWN A 1999 E320 4MATIC WITH 60K.ITS BEEN GREAT TILL LAST MONTH
WHEN DRIVING ANY STEADY SPEED (NO ACCEL) I GET A REAR END HOP-CHATTER FEELING, ALMOST FEELS LIKE ABS IS ENGUAGING AND ONLY HAPPENS WHEN I HOLD STEADY SPEED LOWER RPMS.ALSO FEELS LIKE ENGINE IS GIVING SLIGHT SKIP WHEN THIS HAPPENS.
THE DEALER CHECKED ALL CODES (NONE) THEY DID NOTE- SLIGHT PLAY IN FRONT DRIVE SHAFT BUT FELT THIS WOULD NOT CAUSE A VIBRATION. ROTATING TIRES AND INSTALLING NEW TIRES DID NOT CHANGE NOISE TRANSMISSION FLUID LOOKS GOOD , I WOULD BE OPEN TO ANY AREAS TO INSPECT AND OR ANY HELP ,WOULD BE GREATLY APPRECIATED. THANKS

Welcome to the forum. The search function on this Site is really good. Just put in 'rear end hop' and see what comes up. If I had to guess I would guess the flex disc needs replacing but I'm certainly no expert. Also, turn off your caps when you type, it makes it much easier to read.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

Yes, flex disks probably the first thing to check, front and rear on the propeller shaft. They could be dry/cracked/separating, as mine were. Also, not sure on your motor (m112?) but the m111 in my 230 has a belt tensioner and shock that can vibrate with age/wear, and in my car, it caused the EXACT same symptom you describe under the same conditions.

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL