I have helped a person solve out a booming sound and vibration problem in a W202 which he had bought for cheap, to his advantage he had access to a lift.

The manual tells you to start by first verifying the slip joint is in line, then it says to undo the front flexdisc and rotate the shaft to the tripod one leg and test again. Repeat till all three positions are done at front then repeat at rear.

First the shaft centre bushings were greased - they had grease that resembled glue. fresh grease and a few tests later the shaft suddenly went quiet when the diff tripod was moved 1 leg. I cannot explain it technically why it caused to be quiet - but it did.

during these tests I did notice those flex discs get hot and smell like tires after a highway drive in texas summer. I believe if you can find a truck repair shop they can shed more light on this, box trucks and flat beds utilise multi piece driveshafts.

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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)