The rule of thumb is that a transmission (or differential) noise that comes and goes at various speeds is not too much to worry about. It’s when the noise is constant that you have a major problem. All transmissions wear over time and kilometres, so it’s natural for a transmission to start making a bit of a whine now and then.

Generally, these noises are the result of wear in either the bearings or the meshing surfaces of the gears themselves. If the noise goes away after 80km/h you could just continue to drive the vehicle and keep a note if things change. But if the noise is getting progressively worse or it’s really loud and/or grinding, then you probably need to have the unit checked by a specialist.

The MQ Triton doesn’t seem any better or worse than its rivals in this department. But, like other makes and models, there’s a healthy aftermarket supply of replacement intercoolers and the pipework that feeds them, so it’s definitely not an unknown problem.

But your experience is exceptional. Were all five vehicles bought brand-new at the same time? If so, they’re all likely to be from the same production run which could explain a faulty batch of hoses.

The D-Max is pretty well regarded in the trade for its ability to go the distance, but modern, common-rail diesel technology has shown that a vehicle with fewer kilometres is usually a better bet than one with more. Although they do an amazing job in terms of power, torque, towing and fuel economy, today’s turbo-diesels are pretty highly strung in some ways and really need their maintenance. And the older they get, the more attention they seem to need in terms of new injectors, filters and pumps.

A D-Max with those kilometres might be ready for a pretty big (and expensive) service, too, so make sure your first trip in it isn’t going to be to a workshop. Ultimately, price, condition and service history should steer your decision as they should in any second-hand vehicle purchase. I’d take a vehicle with 150,000km with a full service history over a 60,000km one with no service records.