Not to comment on Xterra, as so far my diff is OK ( only had my truck for 8 months but I had a Jeep Rubicon with a Std D44 with locker and I had 33' tires and wheeled the truck for 50 times in 4 years without problems ( D44 problems I mean ) and my friend is in his 5th year on his Rubicon truck, and he wheels once or twice a week, and he's got 35' since 3 years, and he's very very hard on his truck ( he broke almost everything from driveshaft to anything else, but D44 is still running ). But after hearing all these comments on TheOR diff, starting to get worried, especially that Nissan recommends synthetic oil only for that model, and what's strange they do so in a 75w140 grade even here in cold climate Canada. Every truck I had before, uses 75w90 over here, and 75w140 in the lower states, and none did insist on synthetic ( mind you I'm synthetic all over from diff to tcase, to anything)but concerned Nissan is recommending the thickest and most protective synthetic for their diff, makes you wonder ).