Driveline rumble instant change with speed

Many of these don’t need it for a long time. At least on these MB cars, the driveshaft is essentially straight so there is no flex or movement unless some mount (engine, trans, diff) is collapsed. I had the driveshaft out of my 93 300SD which had about 291K miles at the time, and it moved smooth and perfect. I think for at least some of these cars, if they have t seen too much moisture or salt, the u-joints just don’t flex enough for it to matter, assuming the rest of the driveline is actually aligned.
So if there's "no flex or movement" in the shaft as you stated, why even bother manufacturing a u-joint/cv joint on it?
:unsure:
 
If you can, put the car on 4 jackstands, put it in gear, and walk around it while things turn. Rear end noises have been hard for me to track in the vehicle, but I’ve had luck with this method. This, and perhaps a mechanics stethoscope (broom stick for length to the rear diff) would be something I’d consider.

PS. that’s a beautiful car. I would Love to have some time in one of those
 
So if there's "no flex or movement" in the shaft as you stated, why even bother manufacturing a u-joint/cv joint on it?
:unsure:
Because if the engine or transmission mounts sag, then it isnt straight. At least that’s how it was explained to me.

Mercedes have designed a system where the propshaft is kept straight. The effect of a "straight" UJ is that there is no / hardly any inherent vibration produced by the geometric simplicity of the universal joint.

The crucial thing to note with this Mercedes design is that when the car goes over uneven ground the rear wheels move up and down but the differential does not. The propshaft does NOT extend and contract.

(The up and down motion of the rear (driving) wheels is catered for by four constant velocity joints in the axles)

The whole point of the Mercedes design is that the output from the transmission (which just so happens to be the same "height" as the front of the crankshaft pulley) is at the same "height" as the input shaft (pinion) of the differential.

The resilient mounts on the engine + transmission + subframe (and differential) are important. If one or many of these mounts collapse then it is possible to have a kink in the SINGLE universal joint - you might / will get inherent induced vibrations in the driveline.
 
If you can, put the car on 4 jackstands, put it in gear, and walk around it while things turn. Rear end noises have been hard for me to track in the vehicle, but I’ve had luck with this method. This, and perhaps a mechanics stethoscope (broom stick for length to the rear diff) would be something I’d consider.

PS. that’s a beautiful car. I would Love to have some time in one of those
I thought one was not supposed to spin tires that fast? I need to get to 60+ in order to get the noise.

Drove the car today, was up to 70, and I didn’t notice it… weird..
 
Great point. You can only walk around outside if its at idle rpm, and I personally wouldn’t want to be close to the tires if they were spinning that speed. but you might hear things nonetheless.
 
Maybe this fella is somewhere hiding
1648610151464.jpg
 
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