Need help diagnosing an issue with my 350sdl.

Under acceleration with a decent load - it doesn't have to be floored, but you have to push the pedal farther down than Grandma would- the car has a definite vibration or "shudder" from the rear end.

The driveshaft feels tight and the flex disks look okay. Certainly not new, but not cracking apart, either.

The diff doesn't whine. Rear shocks are new - some idiot put spring helpers in the rear springs, those are coming out ASAP.

Could this be a differential mount issue? CV shaft/axle? How do I check the axles for wear?

I noticed this on my 300d also. When I changed the diff fluid I flushed the diff with new fluid before sealing it back up and little metal shavings came out. They weren't big. It just made the fluid sparkle in the light. The axels were replaced in 05 or 06 I think according to the service recs. I'm interested to see the replies.

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1985 300d smoke silver/red int. (204k) <--Sadie the 80's Mercedes from Hades!
1985 300TD 587 cabernet red/155 Creme (143k)
2007 Ford Expedition EL (54k)

"Seems to me you bought a hobby... not a car" - My dad.

Have you pulled the main drive shaft? The U joints might be binding. With the shaft out, flex the U joints through the full range of motion and see if there is any binding. That would certainly cause vibration under load.

I believe the rear cv shafts are identical, so they could swapped side to side and that may eliminate vibration, as they would now be driving on the opposite faces of the cv joints.

How are the engine mounts, trans mounts, etc?

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I choose to be happy, even when the Mercedes is being awkward, lol

Good advice- I'll have to go through that when I get some free time.