I have this same grinding noise on my 2001 STOCK vehicross. It only started about 2 months ago, and I'm looking at about 36,000 on the odo right now.

This is one of two problems that recently started happening. I let off of the accelerator anywhere from 70-15 miles per hour and it's loud enough for me to hear it over the stereo (which is pretty darn loud). I'm definitely going to take it into the dealership in my copious spare time. I'll post what they find out.

The 2nd problem is a very large hiccup when I'm in 2nd gear and going into 3rd at about 30mph. The tranny makes a big BUMP noise and the VX jerks a little more than I'm comfortable with. Does anyone have any idea what I should suggests to the Isuzu dealership, since our Isuzu shops here in Denver pretty much suck.