Hey guys, new here, be gentle, did a search, nothing seemed to match my case exactly.

1 week ago I started noticing a heavy vibration coming from the back of the truck (2006 4.7L DC, 72000 miles, 2wd).

Here's how it sounds:
wuuuuuuub wuuuuuuuub wuuuuuuuuuuub
and if i go faster
wuuubwuuubwuuubwuuubwuuubwuuub

but its more of a growl/drone and less of a dubstep beat.

I got under the truck to look at the u-joints and found the center driveshaft support bearing to have quite a bit of vertical slop (at least .5" up and down). Is this normal or is that bearing worn out?

I haven't checked the slip yoke to see if it's fully greased yet but that is next on my list.

Can you give me some tips on what else I should check before I take it in for service?

Thanks!

I had to have the rear drive shaft replaced on my '10 tundra due to a worn support bearing for reasons like you are describing. I'm no expert, but I'd say that play is a bad thing and likely causing your problem. If so, it will only get worse with time.
It took 5 or 6 visits to the dealership and hundreds of dollars in other charges causing me to turn a bit Hulk-ish at the manager before they finally figured this one out (or at least admitted it and fixed it). They tried telling me it was mud in my wheels (which I'm all too familiar with), worn tires (which I replaced), mud buildup on the tranny and driveshaft (which I paid to have cleaned, even though I pay to have them lube and torque the driveshaft for me at almost every oil change), mud in the wheels again... GRRRR!

But I'd bet my money your problem is the support bearing in your rear driveshaft.
Good luck!