It kind of goes against the grain a little, but there’s a valid case for listening to your friends and mechanic and driving the car until it stops. Since your car is worth – based on average asking prices – about $10,000, you could easily overcapitalise on a new transmission.

The best advice is to have it checked over by a transmission specialist who will know what to look for based on the symptoms they see. You’re right in that a bad pothole could have damaged a drive-shaft (or a wheel, or suspension component) and the torque converter is also a candidate to produce a fault in the way the car drives. On the flip-side, you might simply find that a service and change of fluid brings the transmission back to full health. Meantime, I’m not so sure about rebuilt transmissions not carrying a warranty. Australia’s consumer law suggests that may not be the case.

Kia informed us that you often drive on unmade roads, which perhaps explains why you have broken the windscreens in your cars. A company spokesman told us that they have only sold one Optima windscreen in the time it has been on sale, and that they have windscreens in stock.

As for the Sorento, they say there are two windscreens used in that model, they have one in stock, the other they don't, but they can get one very quickly if it were needed. Further, they say they have had their customer assistance people contact you to invite you to take your car to your dealer and have it checked for any possible quality issues it might have.

You can have your car serviced by a non-factory mechanic without affecting the warranty, but it can present difficulties if it were to come to a claim against the Kia warranty. You can get into an argument about the competence of the person who worked on the car and whether it not they followed the Kia recommendations etc. But if you have a mechanic you trust to do the work "by the book" then there is no legal issue.