The 2nd generation Xterra has issues with the rear differential going out. This is especially true with the 05. They went to 2 spider gears on the 06 and that reduced the problem, but my rear differential went out at 11,000 miles on my 056, so they aren't immune, and the receipt they gave me showed $2500 for the fix. It was under warranty so I didn't have to pay anything, but if it goes out again not sure where they money will come from since I am no longer under warranty.