Vibration starts at 70mph and keeps going until 75-78mph

What is your question?

I replaced all 4 tires (new tires now). The vibration starts right when I hit 70mph exactly and continues until I hit 75-78mph. Has new brake rotors at front because it would shake real bad when braking (problem is solved with new rotors). but the entire cabin still vibrates at 70mph and sounds like the vibration comes from the Rear part of the vehicle. Tomorrow I'll balance all tires. Anything will be helpful it's just stressing and I already spent too much on the new tires

How long has your 2007 GMC Yukon XL 1500 had this problem?

Since I bought it