In a recent Carsguide you advised a reader that there was no need to replace the timing chains on D40 Nissan Navaras. Well, we have just got our back from the dealer after having both chains replaced after they got noisy. Ours is a diesel and has done 125,000km. Apparently it is an increasingly common problem, and some have not been so lucky and when the chain has jumped one tooth on the sprocket it has junked the engine. The dealer quoted us $2800 for the job, but when we complained Nissan agreed to pay the full cost, despite the car being well out of warranty. When I went to pick up the car they had another three queued up for the same job - and this is not a big dealership. Normally the lower one is the problem, stretching before finally breaking.
We were asked if it was necessary to change the timing chain on a D40 Navara and we correctly advised the reader that it wasn't. There is no requirement to change the chain regularly as there is on engines with timing belts, but chains do wear and sometimes they loosen or even break as we reported in our used review of the D40 a few weeks ago. Of course, when that happens you must replace the chain. It's pretty easy to hear a chain when it's loose, there's usually a loud rattling noise from the front of the engine. If you hear such a noise best get it checked out before you do some serious damage to the engine internals.