This model Hyundai i40 had two different automatic transmissions depending on which engine was fitted. If you have the petrol engine, the transmission will be a conventional torque converter six-speed automatic. However, if your car has the turbo-diesel engine, the transmission will be a seven-speed dual-clutch unit. At which point things change.

These dual-clutch units (and not just Hyundai’s) have shown themselves to be a bit under-engineered in some respects. And when they start to develop wear in the clutch packs, they can definitely start to behave poorly including rough shifting, shuddering when moving off and other problems.

But either way, you are going to need the services of a transmission specialist to determine what’s wrong. Even if you have the conventional automatic version, you might still find it has serious internal wear or failures, but only a detailed diagnosis will tell you the whole story.

On the other hand, you might be lucky and simply have a transmission with low fluid level that will be restored to health by a top up of that fluid. You’ll still need to find from where it’s escaping, however, as this is a sealed system and should not lose fluid over time.

The answer is no, but Hyundai's naming policy was very confusing during the 2010s.

The original i30 of 2007 introduced the alphanumerical naming policy and signified a different approach to vehicle engineering, with a European focus with higher-quality engineering rather than a low price to take on class leaders like on the Volkswagen Golf.

Thus 'i' something became a sort of premium nomenclature, and of course is still used to denote this on models like the i30 and Europe's i10 and i20 small cars There was also the German-engineered i40 midsized sedan and wagon until 2018.

But here's where Hyundai muddied its own waters.

In 2010 the larger, American-market Sonata was rebadged i45 for Australia and New Zealand – even though an 'x' and a '5' rather than a '0' meant crossover or SUV, as illustrated by the very popular second-generation Tucson being renamed ix35 in Australia and some other markets from 2009 to 2015 – though this naming policy was abandoned for the third-generation Tucson from 2015. While strikingly styled, there was nothing European about the i45, and it too returned to being badged Sonata from 2015.

So... i10, 120, i30, i40 and i45 for Australia, but no i35.

Thank you.

The Hyundai i40 has a great reputation in the trade for being a solid, dependable car with few inherent problems. In fact, it’s one of the models that has recently helped forge Hyundai’s overall reputation as a safe bet. The brand’s five-year warranty hasn’t hurt it in that regard, either.

In terms of Hyundai i40 diesel engine problems, the news is good. And that’s largely because Hyundai has been building small capacity passenger-car diesel engines for decades and has the technology all worked out.

But there are a few things to watch out for and those include the propensity of modern, common-rail injected diesels to require plenty of preventative maintenance. If injectors, pumps and filters are not looked after, they can all give trouble down the road and fixing common-rail injection is generally not a cheap pursuit. So make sure any second-hand i40 (petrol or diesel) has a fully stamped service book and that no preventative maintenance has been skipped.

The other thing worth mentioning is that unless you plan to do at least some highway driving, then the turbo-diesel – as nice as it is to drive – may not be your best bet. The Diesel Particulate Filter (DPF) fitted to modern diesels needs a good run at a decent speed every few weeks to ensure that it can regenerate properly. If it doesn’t see this sort of running, it can become blocked and, in a worst-case scenario, require replacement. This is by no means a Hyundai-specific problem and many modern diesels with DPF technology carry the same caveat.

The bottom line is that even though the diesel version of the i40 may squeeze more out of each litre of fuel, it’s not necessarily the cheapest-to-own variant in the long run.