There doesn't seem to be a huge number of similar complaints to yours, Len, but that's pretty cold comfort. You could have a problem with the transmission itself or the electronics that control it. Either way, it could be that the transmission is stuck in high gear as a form of limp-home mode to avoid doing any further damage to itself.

The first step is to have the vehicle scanned for fault codes. Sometimes, a fault will be logged that seems to have nothing to do with the symptom, but can still cause the havoc you're experiencing. Try a transmission specialist first, as it's a fair bet they will have seen this exact problem once or twice before.

Broadly speaking, diesel engines have longer life expectancies than their petrol equivalents. That's because the typical diesel has to be more strongly engineered to cope with its inherently higher compression ratio and heavier moving parts, which also means it runs slower with less stress.

However, the advent of turbocharging and higher diesel engine speeds have also seen some lighter duty diesel engines lose some of that under-stressed longevity, meaning that they're not living as long as some old-school, slow-revving, under-stressed diesels. Modern changes including DPF technology, exhaust gas recirculation (for emissions) and single-rail, high-pressure injection have also contributed to shorter working lifespans in some diesels.

In any case, the life you will get out of any engine is directly related to how well it's been serviced and maintained throughout that life. A petrol engine treated to proper servicing will easily outlast a diesel that has been neglected and abused. As for the Hyundai petrol engine in your van, the rule of thumb says you should be aiming for at least 200,000km before spending any meaningful money on repairs. Again, though, this is entirely dependent on regular maintenance.

From the sounds of things, you need a vehicle that can accommodate the wheelchair as an actual seat in the car rather than having the chair folded and stored for the journey. With that in mind, a van or people-mover is by far the best best bet and the news is good, because there are plenty of choices. For a while there, people were converting Ford Falcon station-wagons for this task, but since the Falcon is no longer made, vans have become the new default vehicle to convert. Which makes plenty of sense.

There are specialist firms around that will carry out whatever conversion you require and tailor-make the ramps, lock-down points and grab-rails you need to make it work for you. Switched on companies will sit down with you and discuss your precise requirements and engineer something bespoke if necessary.

At the moment, the list of car choices is pretty long and includes the new Hyundai Staria, VW Caddy, LDV G10, VW Caravelle, Renault Kangoo, Renault Trafic, Hyundai iLoad, Mercedes-Benz V-Class, Toyota HiAce and, in case you need something really big, even the Toyota Coaster. Some of these companies are also registered as NDIS suppliers.

But don’t rule out a second-hand vehicle, either. There are websites around listing used wheelchair-accessible cars for sale. Some will be ex-taxis, but others can be relatively low-kilometre cars that might just have the exact layout you were looking for.