My 2015 Nissan Navara DX 7-speed auto just touched 5000 km and has two issues. The first is that it shudders a bit between 50 and 60 km/h. Once I rev it and go beyond 62 km/h it's really smooth. The second is a faint rattle at times. It sounds like what older cabs or cars sound like. It's hard to explain this one. Nissan is looking at it at the moment. Do you have any idea what this could be?
It's impossible to diagnose the noise without actually hearing it first hand; the dealer is best placed to sort it out for you. The shudder is something I would be concerned about; it's in the range of city driving and would be annoying. Also, you have to be concerned about it getting worse over time and kays travelled. Certainly press the dealer, and Nisan, to sort it out.