03 ML320 Uniidentified Noise - Ideas?
 

For the past few days have had a rubbing sort of noise noticiable in the cabin from under the truck. Only happens when car is moving, doesn't seem to vary with speed, braking or turning, although it is not immediate when taking off from a dead stop (takes a few seconds, till you get above a crawl speed, then stays pretty consistent). I can't really pinpoint where it might be coming from...thinking maybe driveshaft, differential, wheels...can't really say. Almost sounds like a brake pad stuck and rubbing, but its not - definately not a grinding or squealing sound (yet), 'rubbing' is the closest description I can come up with. Any ideas of where to look/what it might be?

Sounds like a problem with the driveshaft center support bearing, take a look there.

Center Support
 

I had the same problem on mine, my indie MB guy said it was a witch to replace, new seals, rusted bolts etc. I think it was around $700.00 but worth it on this job, there are lots of posts on the center support bearing. When in doubt, shoot it with WD 40, drive it and see if you notice a change in pitch. You could shake mine up and down about 1/8".