Hi Christine. Sorry to hear about your problem with 3rd gear. Since yours is a much newer motorhome it does not sound like the famous 5th gear problem which was an issue on older Fiat Ducato motorhomes. I do think Fiat are offering poor service in your case and in the case of the 5th gear issue. If the gearbox is fit for purpose then those that have the 5th gear repaired would not overfill the gearbox with oil and change their driving style to get around what is essentially a design flaw.
Hopefully someone reading this will have some idea what it might be. I can certainly understand why you don’t want to buy another new motorhome that is based on a Fiat when they are trying to fleece you over £875.00 on a motorhome that has done less than 8000 miles, regardless of how many years old it is. However you do need to get it fixed and so if the warranty has expired anyway don’t put any money in Fiat UK’s pockets, get an independent gearbox specialist to look at it. In my opinion Fiat know there is an issue with the gearbox on some models and rather than feel ashamed and try to fix the problem they try to profit from it. A case in point is the 5th gear on my Ducato which is the same part as used by Citroen and Peugeot. Why were Fiat charging much more for the same part than Peugeot? Naturally I bought my 5th gear from Peugeot to save money and also avoid Fiat from profiting in any way.
If you like motorhoming then you should not let this put you off. By all means become wary and educate yourself about issues with various base vehicles. For example I would consider buying a Fiat Ducato based vehicle again but I would overfill the gearbox and ensure I did not change up to 5th until revs were high and not at all uphill. Many vehicles have a weak point but I just wish manufacturers and dealers were more honest about these.
Good luck with whatever you decide to do. I know I would be furious in your position being the first and only owner of the vehicle with such a low mileage.
All the best
Gary
The Motorhome Vagabond