I guess the ND Miata has transmission issues.

It's a little concerning that trans problems are happening after, presumably, a development period where people actually drove cars on the road.

Which is why I'm thinking it is a metallurgy issue and not something inherent with the design. A manufacturing process got a hiccup or something.

The trans in the ND is going to be seeing a lot of load relative to older units. There's a lot of gear reduction happening in the trans vs. in the rearend. The ND uses a fairly tall final drive (2.87ish) and most of the gear reduction is happening in the transmission. That stresses the case more. Keith says the fluid capacity is lower, that reduces the capacity for absorbing heat. Hotter parts that may be going into more misalignment is a recipe for stripping gears.

Again, presumably the preproduction test units weren't failing left and right, so it's probably not a simple case of insufficient design.

In reply to kevlarcorolla:

I don't see Keith as shruging it off but more the case that he has faith Mazda's good enough to get the problem fixed.

I can't find the post now, but I saw something on Facebook where a guy had written to Mazda, and they replied to him that they will be honoring warranty issues that happened in autocross competition, as long as the cars were in Street or ST classes.

I'm not shrugging it off. It's a serious problem. And it's because it's a serious problem that I'm not worried. If the transmissions were only failing behind turbocharged engines that have 250% of their original power level, or after 200 laps of hard racing - that's one thing. The lunatic fringe blowing parts up is usually left to their own devices.

But it's happening to street cars and stock powerplants. We're hearing about it happening via the enthusiast community, so we're assuming that it's only happening to the online folks. But I'll bet it's also happening to the Sunday drivers as well. So it's very much on their radar, and they'll come up with a fix. Getting all hot and bothered and yelling won't accomplish anything.

And more importantly, it's happening to cars under warranty. That means it's an inconvenience to the owners of those cars but no more. Sure, I'd be upset if it happened to me - but that's what warranties are for. And because it's under warranty, Mazda is able to track the VINs of the cars and even get the old parts back so they're better equipped to find the cause and develop a solution. So that helps.

This problem will be solved by Mazda. They've got the knowledge, the capacity and the motivation to fix it. I'm sure someone will gallop to the rescue with aftermarket gears for $2500 and claim all sorts of improvements, but I'm a bit jaded about some of those claims after busting up a bunch of super duper Quaife boxes.

As for the testing - I do find it interesting that the 2.0 cars were really late in appearing. Japan got the 1.5s six months before the US got cars or even before journalists got a chance to drive them. That tells me the 2.0 was delayed for some reason, that it had a very short transition from prototype to full production. I've been wondering why, and I wonder if too much of the durability testing was done with the 1.5. It might just be bad heat treating for one set of gearboxes, that happens. Or it might be a fundamental design problem. But we'll just have to wait and see.

Who here remembers the 1999 motor failures? They'd suffer thrust bearing failures by about 30k, and thanks to the lack of a real oil pressure gauge the owner didn't find out until it was too late. Mazda said it was a bad batch of machined blocks. All the problem engines are gone now other than a few garage queens, most of them got new engines under warranty.

I expect this will be much the same.

Trans lube capacity is the same as just about every other Miata trans, 2 qts+/-. Gear reduction IS higher in the trans by about 15%, but it seems the gear that is breaking is 2nd, not first. 6th gear is straight through, which should result in lower lube temperatures during highway use as most transmissions use 2 gear sets for top gear.

The thrust bearing issue was due to a too small thrust bearing and dry starts after long sits, along with the clutch pedal depressed. The official "mea culpa"was bogus.

Nope, it's something like 1.2 L. Very small. The diff is 600 mL.

The thrust bearing issue was real, and confined to that one narrow range of engine production. The fundamental design did not change from 1990-00 (they went to a larger bearing in 2001), but we didn't see the carnage that we did in 1999. In 2001, they went to a larger bearing.

In reply to Keith Tanner:

I've changed the oil in my ND, I know how much it takes. I made no comment about the rear.

From the Owner's manual- (Approximate Quantities) Item Capacity Engine oil With oil filter replacement 4.3 L (4.5 US qt, 3.8 Imp qt) Without oil filter replacement 4.1 L (4.3 US qt, 3.6 Imp qt) Coolant Manual transmission 6.0 L (6.3 US qt, 5.3 Imp qt) Automatic transmission 5.9 L (6.2 US qt, 5.2 Imp qt)

Manual transmission oil 2.0 L (2.1 US qt, 1.8 Imp qt)

Automatic transmission fluid 7.2 L (7.6 US qt, 6.3 Imp qt) Rear differential oil 0.6 L (0.6 US qt, 0.5 Imp qt) Fuel tank 45.0 L (11.9 US gal, 9.90 Imp gal) The larger bearing put an end to the failed thrust bearing issue. I believe FM actually measured a number of engine blocks that suffered a failed thrust bearing and found no machining mistakes. If there were mistakes made in machining I'd like to read more details.

Silly me, I believed the guys at Long Road Racing. My bad.

As for the thrust bearings, we're obviously going to agree on that one. The fact remains that a lot of 1999 engines suffered that failure while the 1990-97 and 2000 models did not despite having identical internals, so it was either machining or assembly. And yes, I know the bearing part number supposedly changed in 1999, but we haven't found a 2000 block that uses the new design iirc.

The bearing part number changed in 2001, that's why all the '99 and '00 are included in the factory TSB. The NBs have a stouter clutch pressure plate than the NA's, but the same size thrust bearing.

Then why don't all the guys with ACT clutches have thrust failures?

Ahh, never mind. Have a good weekend.

Keith Tanner wrote: Then why don't all the guys with ACT clutches have thrust failures? Ahh, never mind. Have a good weekend.

They prolly don't let their cars sit for 3 months a year. If it was a machining error how did some cars go 70K miles before a failure?

You have a good weekend too.

Keith Tanner wrote: Then why don't all the guys with ACT clutches have thrust failures?

So it's not just RX-7s that ACT makes ridiculously stiff pressure plates that cause pivot ball failures and fork cracking?

It's amusing to see someone argue Miata with the man who quite literally WROTE THE BOOK on them.

Other than that, I hope that the issue is fully sorted by the time I buy a ND (10-15 years).

Oh, and Keith, last fall when my buddies NC broke the shift fork on the track. You called the problem immediately and spot on, thanks. He's back up and running with the improved design unit in place and driving fast.

In reply to KyAllroad:

Do mean the trans really does hold 1.L?

kevlarcorolla wrote: Keith shrugs it off but its pretty unacceptable for this to happen,I mean its not like mazda has no clue what a portion of the cars buyers do with them.

When they start blowing up on the street or on stock tires then I can see the anger. But autocross with sticky tires or lapping events in a car this light, things are bound to happen.

In reply to wearymicrobe:

Blowing up on the street is exactly what is happening. Furthermore,the transmission should be able to handle the power of a stock engine no matter how driven or what tires.

It is my suspicion that a bad batch of parts made it way into the mix. There is a comment posted on another forum that Mazda are in litigation with the supplier of those bad parts.

Until the design is corrected, owners with failed transmissions find themselves in an uncomfortable situation, like finding a fly in their soup and the waiter saying "don't worry, we'll get you a free bowl out of the same pot." If it's a design flaw, they get another transmission with the very same problem. With more NDs on the road everyday, it's fair to assume that Mazda is working hard to minimize the financial impact.

In reply to kb58:

It has not been established the design is at fault. It appears parts not made to specification are the cause, but that has not been established either.

True, but the situation remains; replacement transmissions are likely no better than the ones they're replacing.

In reply to kb58:

Again, no one knows. I have not read of a replacement trans breaking.

Never fly the A model of anything.

Knurled wrote: I can't think of any rear drive Mazda that didn't have transmission issues. Well, the NA/NB seemed to be okay, but that was because they benefited from ten-plus years of development in that design in the RX-7s. And the 1.6's trans was the same as a contemporary RX-7 with 60% more power and 40% more weight. Stronger, actually, thanks to its different drop gear ratio.

A friend of mine was roasting M-types (n/a FC RX-7) in his ~600hp/500ftlbs FC fairly easily, but we are talking about a 4x output increase. Under stock power levels I read it doesn't hold up the greatest to track abuse. The R-types from the turbo S4-S7s seems to be nearly indestructible, including in my friend's aforementioned car.

Snrub wrote:

Knurled wrote: I can't think of any rear drive Mazda that didn't have transmission issues. Well, the NA/NB seemed to be okay, but that was because they benefited from ten-plus years of development in that design in the RX-7s. And the 1.6's trans was the same as a contemporary RX-7 with 60% more power and 40% more weight. Stronger, actually, thanks to its different drop gear ratio.

A friend of mine was roasting M-types (n/a FC RX-7) in his ~600hp/500ftlbs FC fairly easily, but we are talking about a 4x output increase. Under stock power levels I read it doesn't hold up the greatest to track abuse. The R-types from the turbo S4-S7s seems to be nearly indestructible, including in my friend's aforementioned car.

I've been wrecking the smoothcases since I had 120hp... however the newer the trans, the longer they would seem to last.

The Turbo II and FD transmissions were known for their weak synchros. Granted they were still a lot stronger than when the trans was in the RX4/5 but I remember when the cars were new, people were having to fix failed synchros, and some found that you could replace 5th gear in-chassis. 5th has the biggest rev drop on an FC/FD trans so its synchro lives an unhappy life.

OK. Resurrecting this thread because I'll have cash on hand in about 60 days, so I could possibly buy a new ND. BUT, I can't find anything online that states that Mazda has found the root cause of these failures and implemented a solution. Anyone have any new information?