Odd noise coming from under my 2001 X5
 

So sometimes when driving, when accelerating, I get a noise from under the car that almost sounds like running over 3 or 4 rumble strips. It's pretty reproducible. If I'm in Manual mode, it generally happens between 3rd and 4th gear if I get on the engine a bit. If I speed up a little more slowly I can avoid the noise.

Driveshaft bearing?

This is a 2001 X5 with the 8 cylinder engine.

Anybody have something like this happen???

Hmm. Possibly the centre support bearing. The only way to know is to get under and take a look.
I had a similar rumble like that (but I don't remember hearing it) and it turns out it was the transmission. A fluid / filter change sorted it for 5yrs until it eventually gave up last October. Try a service and stick some Dr Tranny in it too.
At the moment my 01 V8 has a harshness / buzzing vibration /drone at 1700rpm on light throttle which I'm trying to pin down.

You can use an app like this:

https://apps.apple.com/us/app/vibrat...o/id1089589547

To measure the exact frequency of the vibration.

You can do some math to turn mph into feet per second then use 5.7ft per rev to get tire rev/sec.

Multiply that by 3.91 to get driveshaft rev per second. If they match it's almost as assuredly the CSB or GIUBO.