'99 Tahoe Questions - Door Locks, Weird Noise...

[OkTahoeHunter]

'99 Tahoe - Loud Drone at 70mph+

Just picked up a 1999 Tahoe 2-door LT 4X4 to make into a hunting/fishing rig. Runs great and drives great. It was all stock minus flowmaster exhaust and 20" wheels/tires. I put the exhaust back to stock this weekend because the Flowmasters were just TOO loud. Now that the truck is quiet, I am hearing a noise I couldn't hear before....

Once you hit 70mph, I get a very loud resonance sound in the cab. Almost like a very low bass pitch that you would hear from a stereo system with subwoofers. Its continuous all the way up to 85mph. I can let off the throttle and its still there until I get under 70mph, then it goes away. 0-65mph, no noise at all. Truck doesnt vibrate or shake at these speeds either. Drives fine. Just the noise is ridiculous. It will give you a headache. It's almost a roar at 85mph...

Tire or wheel out of balance maybe? Driveshaft? I'm not sure and it's not something I can ignore.
Please give any thoughts or ideas please?

Thanks guys....

 

[luke22494]

possibly rear end or front wheel bearings or both. who knows.