MX5 1.8 Automatic non-working speedo/gbox

Hi all, I hope someone can offer me some advice on the problem I have. I recently purchased a 2001 (mk2.5) MX5 1.8 automatic however the speedo does not work currently and the gearbox does not change gears on its own - it has to be selected manually from 1>2>3. I am guessing that this issue is linked if the gearbox works off the speed the car is doing.

I have so far taken it to two garages, one being an MX5 specialist however they have not been able to fix it even after looking at it for several days. It also seems like this is an uncommon issue as I can’t find any information online and I have even asked a couple of MX5 breakers but they don’t know what controls the speed on these.

Any suggestions would be very much appreciated as I don’t know what else to do. The specialist I took it to said that it would probably need a whole new gearbox because they think that a sensor inside the gbox itself is likely in need of replacement on my car.

Many thanks,

There is a comprehensive Mazda produced workshop manual that includes the Auto gearbox on the Mellens site. I am not sure of the link as I downloaded it onto my PC as a pdf file

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I would talk to an automatic transmission specialist, preferably one that’s experienced with Japanese gearboxes. They are far more likely to have an idea of what’s gone wrong and if it’s worth fixing or just replacing the box.

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Thanks for pointing me in the right direction, I’ve been able to find this:

I’ve only looked at it briefly but it seems as though there is an input and output speed sensor which appear to be inside the gearbox.

Thank you, yes I agree that’s probably the best option. The specialist I took it to said that the gearbox would most probably need to be stripped anyway to get at the speed sensor inside so perhaps cheaper just to replace the whole gearbox.

I don’t know how much difference there is between the NA and NB auto, paging @Scottishfiver who has experience in these dark arts.

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I believe there are pretty big spec differences of Mk2.5 & old Mk1s.
Most of my speed sensors are external.
TBH, I’m actually in the process of buying a complete '93 Jatco autobox for my Mk1 just as one sensor, the one that engages O’d appears goosed.
I say appears, the car is being returned to an autobox “expert” however, even if the fault transpires to be a sensor, getting a new one is essentially impossible just now.
It can come via the Main Dealer from Japan at £120.00. The issue is…a combination of the B word and Covid is causing international shipping havoc.
The OP’s issue is entirely different. My box is bang on through 1-3…smooth and seamless. It’s just minus O’d.
That’s the issue I think the OP is going to have as well…“Yes it’s that sensor but we can’t get it”
Mk2.5 autos have their own ECU…I think it’s behind the passenger seat so that’s a possible check point.
In the event another 'box will not be cheap…partly as these people know you are over a barrel. Depending on who you talk to, around £250.00 to £450.00 plus palleting…which a lot of them won’t do.


Thank you both! Sounds like a bit of a nightmare and yeah I imagine getting a replacement sensor will be a big challenge as I couldn’t find any anywhere. My OD is also non-operational but again could just be because the gears themselves aren’t working. I would actually like to convert the car to a manual as it has very low mileage but it’s not something I’d be able to do myself and the labour charges I imagine would be extortionate.

I know it sounds daft, but a crucial thing with them is bang on ATF levels.
If it’s even a couple of litres off the total 6.7 odd , it can confuse sensors,
In my event today, I’ve had to buy a complete box…

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Appreciate the suggestion, I think the previous owner had the same idea as there’s an invoice for the gearbox oil being changed a few months before I bought it. Is it difficult to check if the level is correct?

There is a Googly process.
Basically involves up to working temp, go through the gate to swish it all around…then summat like into N for the dipstick checks. That’s a rough description!


Have another look at the pdf you found - page 31. There are separate speed sensors attached externally to the gearbox.
What do you want to do about this?
A colleague has converted a MK2.5 auto car
like yours to manual. Alternatively you will probably need to source sensors to start with and possibly a replacement gearbox.
MK2.5 auto gearbox is completely different part to that fitted to the MK1, apparently.