I have a D40 and over time became disappointed with the strength of the chassis. But then I found all dual cab makes suffer from the same problem. About where the cab and the tub meet there is lots of chassis flexing. This does not happen with sedan style 4wd’s because they are all one piece.
Also without modification, the d40 can’t carry much. Most others cannot either. The d40 is not more than average here. After a GVM upgrade they become useful.
Around town, coastal roads, no probs. But outback even bitumen roads 80klm max. Care must be taken not to flex the chassis or it will eventually bend/break. Hit a whoop de do, too fast with a load and that’s you chassis bent.
I had Superior Engineering weld in chassis strengthening plates as a precaution. I still keep the speed down on unpredictable (outback) roads.
As far as the engine, gearbox etc goes they seem to be reliable at least the 3L V6 that I have is fine. Chassis strength and load carrying are my only concerns.
Stock standard is good. I have a steel bull bar, side rails, under body protection, winch, 2” lift etc. If I was doing it again, I would just fit a nudge bar and nothing else, it’s all too heavy. It all subtracts too much from the gvm. I would go for a gvm upgrade which probably also means a 2” lift as part of the upgrade.
I recall the 2.5L has an issue with the timing chain that needs to be replaced about every 120,000klm as a precaution? Someone else can comment on this as I am not sure of the details.