Chirping Noise and Vibration

I have a 2008 Toyota Tacoma 4x4 Crew Cab TRD Sport with 53,500 miles.
Lately my truck has been vibrating pretty good when I'm around 2000 RPMs. Vibration happens when accelerating and when cruising at speed, but always seems to be around the same RPM and is independent of speed. When I take my foot off the gas, the vibration goes away. Vibration only happens when drive is in gear and truck is moving, no vibe when stationary or not in gear.
Also, when I punch it from a stop, I hear a chirping noise from what seems to be the front right of the truck. Sounds like metal on metal. Sound only present when I really punch it. Under "normal" acceleration, there is no sound.
I just had the tires replaced which helped to reduce the vibration, but its still present. Also, the chirping is still present. I asked the mechanic at the shop to take a look at the u-joints when they were replacing the tires, but they checked out ok. Not sure where to look next. Any thoughts or questions

 

how about the carrier bearing?

 

is it noisy in 4wd?

 

I was told by the shop that my whole drivetrain looked good. How would I check the bearing myself?

Also, I haven't tried to drive it in 4wd since this started happening. I'll try it this afternoon and post back.

 

I just took it out again and I still get the vibration when in 4wd

 

UPDATE: took my truck to the dealer to have it looked at...

The rear drive shaft was out of balance / bent so the whole thing needed to be replaced. Fortunately it was covered under the powertrain warranty. Once they swapped it out, the truck drove like it was brand new.