The problem could be in the gearbox selectors which, as their name suggests, are the mechanical linkages that allow you to select each gear. If the selectors for fifth gear are worn or incorrectly adjusted, you could have a situation where the car is not fully selecting fifth gear, allowing it to pop out of gear when you load the transmission.

The other possibility, of course, is that, at 428,000km (a pretty good innings for one of these vehicles) the actual internal bits of the gearbox are so worn that the thing is jumping out of fifth in protest. If that’s the case, an inspected, second-hand replacement gearbox from a wrecking yard would be the most cost-effective solution.

None of the vehicles you’ve listed are exactly low-maintenance units. They all have complex all-wheel-drive drivelines (which will be appreciated when towing a heavy trailer across a wet showground) and they use the latest common-rail diesel technology which is fairly intolerant of poor servicing.

As for a power tailgate on a ute, I’m afraid you’re out of luck. But some of the wagon versions of these vehicles can be optioned with powered tailgates. The catch there is that these vehicles use coil sprung rear axles (as opposed to the leaf-sprung ute versions) so they’re not as adept at towing. The Toyota Fortuner, for instance can’t match the HiLux’s 3.5-tonne limit and makes do with 2800kg; not enough for your requirements. The Ford Everest (based on the Ranger) is a little better at 3000kg, but still trails the Ranger’s 3500kg towing capacity and is right on your self-imposed minimum.

Petrol is really the best in your situations diesels are not at the their best in stop-start driving. I wouldn’t suggest a Great Wall; I feel they are still to earn their stripes in this country. Go for a 2.7-litre petrol Toyota HiLux.