ND first gear problem

[John_M]

@Parker

 I’d like to ask the cognoscenti amongst you whether or not I should be concerned about the durability of the gear shafts and teeth in the Auto box which has apparently been designed specially for the SkyActiv 2 litre? 

'Cog’noscenti, very good!  I’m not, but…

I assume it’s a torque converter-equipped gearbox a bit like this

Skyactive auto

with planetary gearsets, rather than an automated manual, so the design will be completely different to the manual.

I suppose that if you take the view that Mazda has deliberately designed the manual ‘light’ and rather overdone it, and has taken the same approach with the auto, then you might think that is ominous - but I wouldn’t extrapolate in that way.  And I would expect it to be more reliable than any sort of dual-clutch transmission such as the DSG or Powershift. [see second edit below - the auto is not a new design gearbox]

EDIT:

Another thought.  One reason that has been suggested for the supposed fragility of the gearbox is the low reduction final drive, which puts more torque through the gearbox than would otherwise be the case.  Could the same apply to the automatic?  The final drive ratio on the manual is 2.866.  On the auto it is 3.454 which is more favourable in this context.  However, using the brochure numbers the overall ratios for the auto look very different to the manual so a bit more digging (or a real expert) might be required.  I’ll crunch a few numbers (not gears).

EDIT 2:

I have done gear tables and on the brochure numbers the auto gearing appears to be much  ‘longer’ even with the higher diff reduction so maybe I have missed something  - it looks as if the auto needs more reduction overall to end up with even vaguely similar gearing to the manual.  Perhaps somebody else can solve that one.  Meanwhile, I unearthed a reference to the gearbox type being the SJ6A-EL.  This is not a new gearbox, it appears to have been in use for the MX-5 since 2006 and on the RX-8.

E&OE, I am not an automotive expert of any kind so please don’t rely on any of the above.  Perhaps a real expert will come along to solve the gearing question, or find my mistake or wrong assumption. 

 

[John_M]

Here are the gear tables based on the brochure figures in case anybody is interested  - auto in purple, manual in green - as you can see the auto is much taller geared if these numbers are right, and would imply that maximum speed is reached in 4th (auto) or 5th (manual).  Can that be right?

Ignore the ‘Add. Red.’ column - that was for me to play with.

I’m fairly sure my numbers are about right subject to the info given, and using standard 2.0 size tyres 205/45R17 of 24.24" diameter.

Sorry about the drift I have got into trying to give an opinion on what looked a simple question, to which the short answer is -  I can see  no reason to expect a problem with the auto box.

[Parker]

Thanks very much for doing all those calculations John . It’s good of you to take the trouble.

I particularly like your bottom line, which is reassuring.

[dogman]

Dealer rang for car to be left in. Gearbox to be stripped to investigate.  Rang Mazda UK to say not happy but that is procedure.  Asked about new gearbox but because it is an unknown problem they have to investigate. Being given a loan car and dealer says it could take up to 2 weeks. Not a happy bunny and good luck to the rest of you.

[John_M]

@dogman

Dealer rang for car to be left in. Gearbox to be stripped to investigate.  Rang Mazda UK to say not happy but that is procedure.  Asked about new gearbox but because it is an unknown problem they have to investigate. Being given a loan car and dealer says it could take up to 2 weeks. Not a happy bunny and good luck to the rest of you.

I would take that at face value, although your dealer doesn’t sound to be jumping around to help.  It’s under warranty, it’s almost unused, they’ll fix it presumably, let’s hope with a replacement gearbox if that is what you want.

 

[dogman]

Car now not going in until 23rd due to mechanic being off. Well done Mazda.

[AJred]

Having followed this gearbox issue for several months on the US forum,where there is much more ND activity generally,I wonder if Mazda UKs stance is because your car is a mid 2017 and presumably has the version 3 gearbox.
In the States there have been numerous gearbox replacements (mainly for cars autocross/raced) and it seems that Mazda over there change them without any fuss.However, the feedback seems to be that the latest version is holding up so far(fingers crossed!).
Maybe your issue is a different problem,hence wanting to analyse before just putting a new box in.
There are a number of negative comments on this forum ,mainly from people who don’t own an ND, which imply this is a big problem.I asked under a different thread for details of actual failures and whether any affected 1.5 cars but only got comments regarding the raced Rodders cars and mention of possibly some others. I am not saying this will not affect us all at some point but so far there is very little actual data concerning numbers and details. Since owning my ND I have gone out of my way to engage other owners and have been met by complete disbelief when I have asked if they had been aware of a possible weak gearbox etc. I have spoken to my dealer,who I know well at a senior level,and they claim to have had no problems so far.
I hope the op gets his car back fully sorted very quickly and look forward to reading what the issue is.Clearly the delay from the dealer is not helping .

AJ.

[Mad_Malc]

 I also checked with my dealer and they have not had any issues with ND gearboxes. Hoods yes, gearbox no.

 

[Gerryn]

@Mad Malc

 I also checked with my dealer and they have not had any issues with ND gearboxes. Hoods yes, gearbox no.

 

Ian - by ‘hood’ you mean 1) bonnet or 2) soft top? That needs some clarification in my mind?

Gerry

 

[Gerryn]

@John M

Here are the gear tables based on the brochure figures in case anybody is interested  - auto in purple, manual in green - as you can see the auto is much taller geared if these numbers are right, and would imply that maximum speed is reached in 4th (auto) or 5th (manual).  Can that be right?

Ignore the ‘Add. Red.’ column - that was for me to play with.

I’m fairly sure my numbers are about right subject to the info given, and using standard 2.0 size tyres 205/45R17 of 24.24" diameter.

Sorry about the drift I have got into trying to give an opinion on what looked a simple question, to which the short answer is -  I can see  no reason to expect a problem with the auto box.

Don’t know much about gearing, but surely the manual transmission is ‘Taller’? ie - higher eared? No Auto Trans is faster than a manual - losses in the auto box account for the difference. The lower diff gearing on the Auto surely means lower speed in any gear, not faster than a manual? Looking at NBFL differences at this point. I’ve never seen an auto box (in any make of car) go faster than a manual trans. - Ask Rodders if he’d prefer an auto box!

 

 

[Mad_Malc]

@Gerryn

@Mad Malc

 I also checked with my dealer and they have not had any issues with ND gearboxes. Hoods yes, gearbox no.

 

Ian - by ‘hood’ you mean 1) bonnet or 2) soft top? That needs some clarification in my mind?

Gerry

 

 Hi Bob,

I am Malcolm not Ian, I know we look like identical twins so it is easy to confuse us!!!

I am English so a hood is a ‘soft top’ and a bonnet is something you wear at Easter!!! 

I will now make an appointment with my psychiatrist.

[John_M]

@Gerryn

 

Don’t know much about gearing, but surely the manual transmission is ‘Taller’? ie - higher eared? No Auto Trans is faster than a manual - losses in the auto box account for the difference. The lower diff gearing on the Auto surely means lower speed in any gear, not faster than a manual? Looking at NBFL differences at this point. I’ve never seen an auto box (in any make of car) go faster than a manual trans. - Ask Rodders if he’d prefer an auto box!

 

Terminology Gerry. Do you call 4th a higher gear than 1st, as I do?  But 4th has the lower ratio.

Higher ratios in the manual box yes, but these are reduction ratios.  The engine spins faster than the wheels.  There’s a reduction at the gearbox (apart from the direct gear and the overdrive gear(s)) and a further reduction at the differential.  The net reduction ratio is the two multiplied together.

The auto has more reduction at the differential, 3.454 vs. 2.866, but less in the gearbox - e.g. in fourth, 1.000 (direct, no reduction) vs. 1.594 for the manual which more than offsets the extra reduction in the diff.

Look at the speeds per 1000 rpm.  I had expected to see broadly similar speeds per 1000 rpm between the two, even though it is common for autos to use a high (as in long, tall) top gear to help with economy.  This auto appears to be effectively a  four speed box with two overdrive ratios, vs. the manual which is 5 speed plus an overdrive 6th (yes I know 6th is direct in the box, but maximum speed is reached in 5th).

I thought perhaps the data were wrong, and maybe they are*, but looking for corroboration now you have put me on the spot  automobile-catalog.com quotes the same data as the brochure and comes to almost exactly the same results as I did for mph/1000rpm in gears.

If you want to check the link for yourself then you will have to navigate to each model, and then drill down to ‘full specifications’. The link points to the ND RF 2.0 page.

E&OE - it’s still possible I have got something round my neck! 

You’re quite right of course about the auto box losses and the auto is indeed slower both in acceleration and top speed.  Because the ratios are net higher, gear for gear, you would be using lower gears in the auto if you were trying to keep up with the manual - you would be in fourth when the manual is in fifth, for example.

*what we need is somebody with an auto to check the speeds per 1000 rpm. 

 

[Gerryn]

Malc -

Werry Intereskin - so what do you call the tin lid over the engine?

Oh and I’m Gerry - not Bob - dunno who he is? Sorry about the name mistake BTW.

[Mad_Malc]

Hi G,

No need for an apology, just messing about as you clearly know.

The aluminium (must be pronounced ‘al you mini um’) cover over the engine of an MX5 is most definitely a bonnet. It is still a bonnet no matter what it is made of if the engine is up front. If the engine is any where else it is an ‘engine cover’.

Have good weekend.

[Gerryn]

H’mm - I can see where you got that name from!
You have a good weekend too!

[Parker]

Thanks very much to Gerryn and John M for taking up the subject of the auto 'box.

As somebody who has trouble getting his head round the technicalities of ratios and diff reduction etc., can I ask a simple question please?

Do you think the auto 'box more, less, or equally likely to break (than the manual) due to loadings on the bits whirring around inside it? 

Sorry to bring it down to such a base level!    I appreciate that the auto is slower and, in the eyes of many, less desirable, but my left leg begs to differ, which is a nuisance.

Thanks again to John for having given his opinion on this already.

[IanH]

@Parker

Thanks very much to Gerryn and John M for taking up the subject of the auto 'box.

As somebody who has trouble getting his head round the technicalities of ratios and diff reduction etc., can I ask a simple question please?

Do you think the auto 'box more, less, or equally likely to break (than the manual) due to loadings on the bits whirring around inside it? 

Sorry to bring it down to such a base level!    I appreciate that the auto is slower and, in the eyes of many, less desirable, but my left leg begs to differ, which is a nuisance.

Thanks again to John for having given his opinion on this already.

 

I think the auto box is an existing one not a brand new design as the manual, certainly not seen any failure reports from an ND auto…

[John_M]

@Parker

Thanks very much to Gerryn and John M for taking up the subject of the auto 'box.

As somebody who has trouble getting his head round the technicalities of ratios and diff reduction etc., can I ask a simple question please?

Do you think the auto 'box more, less, or equally likely to break (than the manual) due to loadings on the bits whirring around inside it? 

Sorry to bring it down to such a base level!    I appreciate that the auto is slower and, in the eyes of many, less desirable, but my left leg begs to differ, which is a nuisance.

Thanks again to John for having given his opinion on this already.

To Ian H’s comment, yes, sources quote the same automatic  6 speed gearbox identifier for the NC and ND (not at my fingertips, but I quoted it upthread somewhere). By way of corroboration, already having the mini-spreadsheet available, I did manual and auto gear tables for a 2012 MZR 2.0 car yesterday and the gear ratios for the auto are identical to the ND. 

The NC diff is higher reduction at 4.1 vs. 3.454  for the ND auto, so the overall gearing is taller for the ND.  This is not unexpected as the NC makes its maximum power at 6700rpm, vs. 6000 for the ND.  Maximum torque for the 2 cars is similar (ND 200Nm, NC 188Nm).  For the same power at the wheels, the torque through the gearbox will therefore be a bit higher on the ND than the NC, but the difference in final drive reduction from NC to ND is less on the autos than the manuals;  and the gearbox is a known quantity, unlike the new gearbox on the manual ND.

The auto population will be a lot smaller for the auto than the manual (maybe there is a meaningful number of autos in the US?) so any particular problems with the auto on the ND installation might take time to become apparent.  However, this type of planetary gearbox is generally well developed, the same model has been in use for some years, and it would be surprising to me if there were to be any new problems with it, if properly maintained and subject to normal use. I haven’t searched for historic problems on the NC.

I can’t see anything in the service schedule about changing the automatic transmission fluid;  I’d be looking further into that if I was keeping one long term.

My gear table calculation for the 2012 2.0 is here

Note that I have no special or inside knowledge of these cars - this is just based on available information and my non-expert opinion. 

[dogman]

New gearbox being fitted.