What do your service managers say is the proper time to do this? I asked the one at the dealer I've been going to and he said Nissan does not recommend changing and that he has some customers who have 100,000 on their rear diffs without ever changing. I don't have the manual handy but I seem to recall every 30,000 miles unless you drive in harsh conditions and then every 15,000. I was planning to change at 15,000 on the better-be-safe-than-sorry theory and was very surprised to hear him say this.

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