I just finished replacing the front and rear wheel bearings (and a whole lot more) on my daughters 2006 Liberty 4x4. Took it for a test drive and still am hearing a very noticible howling noise. I thought for certain it was wheel bearings since they are original and had 140k miles on them. My next thought is U-joint on the drive shaft, but not sure. A basic inspection, they did not appear to be any play and I do not get the typical clunk noise when putting into gear. Any thoughts on how to further isolate this? The noise is the same when in drive or neutral coasting and in both 2 and 4wd. Hoping it's not the rear diff pinion bearing, but not many things left it could be. The ring gear looked fine upon inspection when I pulled the axles. Thanks in advance.