Decent video where he talks about the ND gearbox oil, and his results when he used an alternative.
Guy’s a driving instructor. I’ve watched some of his driving vids to brush up on my own skills (you’re never too good to improve your driving skills)
I agree with his comment about Mazda UK telling him it’s 75w-80 in there. They told me the same when I emailed them.
Interesting how he thought the MIllers 75w-90 was a nightmare when cold.
It’s interesting too how he comments on the more recent failures on later models. He touches on the KPC theory, a ‘conspiracy theory’ mentioned on the US forum, as an idea of the more recent failures of later NDs.
I have some Castrol 75-90 at home as recommended here and it has made me hold off putting it in.
I noted that Febi do a 75W-80 gearbox oil you can buy as litres…
The reason you don’t see any failures on Richard’s ND2 is because it has a DMF which reduces shock to the geàrbox plus a reduction in torque. As regard oils because the gearboxes have variable build qualities different oils will react differently. Whatever oil you use it should be a fully synthetic one (and the Mazda one is not) as the gearbox can see temperatures of 240⁰ .
My 2016 Recaro still has a V1 gearbox so on the advice of Walter Motorsports I use a 75w/140 in it (Millers CRX 75w/140 NT+) and hopefully it will keep the gearbox from exploding.
The biggest issue that contributes to gear box failure is not what oil you use but ABUSE. After a short period of ownership It was clear to me that the gearbox did not react well to very fast gear changes. Yes it is a very good gear change, smooth and slick, but it does not take kindly to being ‘rushed’. You can change gear, without damage, much faster in an old A40 Farina than you can the ND.
My car is 7 this year and due it’s service. I’d like to swap out the gearbox oil for peace of mind but it seems like a minefield. The box is running sweet with only first and reverse difficult to select from a cold start.
That might explain the almost total absence of failures on '19-'21 cars (which his '70 plate resides), but don’t explain the faiures reported on cars AFTER this date. They will still have the DMF too.
The way one drives never seems to get mentioned when talking about gearbox problems. Surely forcing through a quick gearchange with cold oil will put a higher strain on the selectors and synchro cones than showing mechanical sympathy. The general public has often proved to be a harsher test of a car than factory endurance test drivers.
That chimes with the story we were told on one of the R&D courses. I don’t know if it’s true or not, but looking at some modern products I can see when the ultimate “consumer” test was skipped. And I always ran that final test.
The story then, roughly as we were told it.
When one of the first portable domestic electric vacuum cleaners was being readied for public release press announcements after extensive testing in R&D and the factory, some wives heard about it, and asked if they could have a quick play with the six pre-production prototypes.
Those normal people managed to inadvertently break all six machines within a couple of days, and in ways the designers never believed possible, but were actually highly likely in a normal house, with stairs to fall down and doors to trap leads etc, and children and pets chewing and leaking, as just a few of the recorded fail points.
It was almost a year before the third and final batch of prototypes passed a month of real life testing.
They went on to be world leaders.
I get this, and add to that the odd poster in the past hypothesizing that the failures could be due to US owners not being as conversed driving manuals!
However, both points don’t describe the literal hiatus of failures on '19-'21 cars. Essentially none. Unless of course every one who purchased an MX5 in that period was gentle with gear changes and were conversed at driving manuals!
Looking at the poll running on Miata.net, the cars with the least amount of failures are 2017/18 at 4 replacements compared to 13 for the 19/21 cars, so it can’t all be the DMF improving the issue.
I thought of that myself actually. But a poll is a snapshot of ‘now’. Meaning many a user who has reported stuff over the year may well have moved on and are in some other car, not posting on an MX-5 forum anymore.
Ha! That reminds me of my student industrial training days at Morphy Richards (the domestic appliance manufacturers) in South Yorkshire. The irons manufactured there were developed using all sorts of “drop test” rigs which the irons had to survive. However once in production we had a return from a customer complaining that her iron had broken after being thrown down the stairs at her husband
