Chevrolet: 1999 Tahoe, slip yoke, tire noise

Question
Hi. I have a 99 Tahoe (4 door with 4 wheel drive) when Im driving down the road or highway (in 2wd) it makes a Humming sound, with the windows down its not any louder. when I put the truck in nuetral (while goin down the road) it will stop. also I can fluctuate the sound with the gas pedal. I ampositive it isnt tire noise, and I am woundering what your thoughts are. Also the truck has the notorious clunk noise, form the rear when starting and stopping, which Im told is from the slip yoke being dry. do you think this could be related???? Any thoyughts would be much appreciated. Thanks!

Answer
CHUCH;
 Hi  - well first off I would have  the yoke and bearings checked, you do not wish for them to blow when you are driving it, you will have a tow bill and than what ever they will charge you to repair it, as you will be stuck. And if you are lucky it will not fly off and hit some other car or window and than you will have more to pay out. I would check the fluid level as it might have the original fluid still in it, or have it drained and replaced.  ok