This is not necessarily a problem, but rather a characteristic of modern, multi-ratio transmissions. They can give the impression that they’re constantly searching for the right gear for the conditions, and it’s worse in hilly country or if you’re towing something. By constantly trying to be in as high a gear as possible, the engine will theoretically use less fuel.

Probably the real question is why a computer-controlled turbo-diesel engine needs an eight-speed transmission in the first place. The answer is that it’s all to do with recording a better fuel consumption number than your opposition on the official test. Sometimes, the vehicle has more gears than it can actually use in Australia. Our 110km/h freeway speed limit meant that early examples of the Toyota LandCruiser 200 Series (which had `just’ six gears) wouldn’t shift into top gear. That’s because the factory calibration told the transmission it could only use sixth gear at speeds of more than 115km/h. Which, just wasn’t happening for the vast majority of 200 Series owners in this country. A reflash for the computer fixed the problem, allowing the Cruiser to select top gear at closer to 90km/h, but it’s a great example of where transmission tech is heading.

This problem has occurred before and happens when the pulley rubs through the hose, which finds itself in the wrong position under full turbo-boost. From what I can gather, the problem is due to a running change in supplier of this hose. And even though the hose was a slightly different shape, the manufacturer used the original alignment marks from the previous hose. So, when the mechanic fits the new hose, it places it in the path of the fan pulley when the engine comes on boost.

Ideally, the hose needs to be fitted so that there's at least 25 or 30mm of clearance between itself and the pulley. Your twist-at-the-bottom method should work, because you're effectively altering the incorrect alignment marks to where they should be.

You have a very common-sense approach to this Neil, and I agree with your theory 100 per cent. Towing a heavy load in an overdriven gear – whether it’s a manual or automatic gearbox – is not a great idea. Some gearboxes are obviously stronger than others, but even so, I reckon it’s just a good policy based on the principles of mechanical sympathy.

Towing in overdrive places huge stresses on the mechanical components of a gearbox – a piece of equipment that already has its back to the wall with 2.3 tonnes of caravan trying to drag it to a stop – and limiting the load and stresses by sticking with a ratio no higher than direct-drive (1:1) just makes sense. Think of it like your legs when riding a push-bike: Using a higher gear is fine until the driveline starts to load up, such as when climbing a hill (or towing a caravan in your car) at which point you need to shift to a lower gear to avoid your leg muscles exploding.

You’re right in suggesting that your car heads for the higher gears in a hurry to reduce fuel consumption, and this is one of those times when the manufacturer has placed the official fuel-consumption number on the windscreen sticker over common-sense. Not that Mitsubishi is the only offender (far from it) but it remains that the engine and gearbox have been calibrated for maximum fuel economy rather than maximum mechanical sympathy.

Ands let’s be honest, with a big caravan hitched up behind, no vehicle is going to record brilliant fuel consumption figures, is it?