"waa waa waa" sound between 60-70 mph?

I have noticed a loud waa waa waa sound coming from the rear end of my truck at around 60-70 mph, it only does it while I'm on the gas, if I let off it goes away. I noticed it will do it around 40mph around the same rpm range (2400-2600). So I'm assuming this isn't not a tire issue. Any advice? Getting sick of hearing the waa waa waa band in the back of my truck on my hour commute every morning. Truck has 118xxx on it. 07 tacoma 4x4 sport 6speed.

 

Is it the blond chick in the passenger seat? Mine makes that sounds sometimes. Seriously, it's probably a U-joint or carrier bearing on the driveline. Pretty easy fix if you are mechanically inclined.

 

mine does the same thing, and also since i installed spindles i feel weird vibrations at that speed and nothings loose ive checked and tightened everything a couple times

 

Haha! My girlfriend (who is blonde) will enjoy that post. Thanks, I will check it out!

 

Also it will vibrate while under power from about 50-65....same issue?

 

Check the carrier bearing. Slide under your truck and grab the driveline. If it's sloppy the carrier bearing needs replaced. If you haven't greased the U-joints in a while and they're worn they will need replaced as well.