This may sound a little wacky but it might just be your tires. The first owner of my 05 WK managed to wear the sr-a's out in 18K miles. If yours have been run too soft or hard they could have deformed tread. Check the tire closely. See of you have any cupping or un even wear. Were the tires just rotated, fronts are generally noisier than rears. I'm not thinking that after 17k miles that your rear axel is failing, though it is possible. If you suspect the rear end, by all means.. have the fluid checked.
If your tread is worn, go get new tires. If not try rotating and see if the noise moves to the front.
05 Grand Cherokee Limited 5.7 Hemi 265/65/17 Revos, K&N
HEMI CLUB MEMBER #10
1998 ZJ Special Edition 2wd- Traded
1991 XJ 2.8 2wd Sold