I have a 1999 gmc suburban 80k mikes with a 6" rancho lift lt285/75r16 tires 4 button 4x4, 4hi, auto4, 2hi, and 4lo when I drive down the hiway It starts making revving noises.The noise will slow down to sound like a bearing and then rev up and down, but the tach and feel of the engine never change. If I remove the front driveline the noise goes away and the truck drives and sounds normal. Here is a list of parts I have changed

It almost sounds like the transfer case is trying to engage ???


transfercase (used)
front diff (all new bearings, same gears)
cv axle lf (new)
lf hub bearing (new)
frt driveline u-joints (new)