2000 tahoe limited vibrating at high speed

[mason704]

my tahoe is starting to vibrate just a little bit i just bought it 2 weeks ago and only does it around 70-80 mph and is not bad enought to be tires out of ballance nor does it feel like it i read haynes manual and it said to shift gear at the same speed and if it continues it is not the driveshaft but im thinkin it is, when taking off from a hard start there is a noise not like a clunk but another type of metal noise but if i take off easy it does nothing anybody had these issues