Thanks! I've enjoyed it so far. With low gas prices, it's actually been cheaper to operate than my Frontier was in 2012.
At around 1500 miles, I noticed a whine sound coming from the rear end between 55-60mph, but only on throttle. I took it in to the dealer and they inspected the axle. The oil was fouled and it was full of a thick, metal sludge. So Nissan replaced the axle under warranty. The new axle did the exact same thing. I brought the truck in at about 4k miles. They found the same thing, oil filled with metal.
So, Nissan replaced the axle again. My current axle now does the same thing, only it whines both on throttle and off, from 50-60mph. That started around 4.5k miles. I'm going to have to take the truck back in, and I'm sure they will find the same issue. Fouled oil and lots of metal.
I think the problem is the oil is overheating (causing the fouling) and it's causing the spider gears to scale (causing the metal shavings). Dana makes the rear axle assembly, and their quality control has been bad the past several years. Nissan has not kicked up much fuss replacing the axles, but as we get closer to lemon law limits, I'm not sure what they are going to do.
The dealership now ignores my emails, which is not an encouraging sign. I expect to get some pushback when I bring my Titan in again, especially since it's for the same problem. What makes me nervous is the thought that all of the axles are defective right off the assembly line. It's a bad manufacturing process for the spider gears, and there is no reliable replacement under warranty.