MFactory upgraded gearsets
 

I have asked MFactory to consider designing a stronger gearset for the Miata transmission. There would need to be a concensus of which trans and most desired gear set before anything can be moved forward on.

I believe that the 6 Speed trans is a better platform to start with due to what appears to be a more rigid case design, I would like to hear what others think.

The most common gripe about the 6 speed box is that it is too short, especially 1st gear. With the rather wide availablility of rear choices 3.6-4.7 one would likely be able to fix that if so desired.

The 5 speed trans is MUCH cheaper and abundant, is said to shift much smoother than its 6 speed counterpart and replacement parts are much cheaper and are more widely available.

I would like to hear what everyone else would like to have is possible and gauge interest before wasting anyones time or money.

Obviously MFactory will need to set prices but they will first need to know what everyone expects.

I vote for five speed. I like it smooth and cheap, like so many other aspects of my life. ��

Follow up question. Is it the gear edge strength or case flex that cause 5 speed failures?

There is the Quaife option available for the 5 speed now. Helical cut gears are designed to produce little axial force.

Straight cut gears vs helical | Automotive Thinker - Discussing the finer points of automobiles

So I don't want to be a debbie downer, but I am doubtful that this will go anywhere. Quaife had a "stronger" gear set for sale for a good while for the 5 speed. It was very expensive and eventually turned it out it was not much stronger then stock. FM dropped selling them due to issues. What I am trying to say is I am betting this will end up being far more expensive then expect, not as strong, and you probably won't get enough people willing to put up money up front to get them built. At least not at a price point that will make it competitive to the T5 setup that TSE is working on.

From a marketing perspective, I would think a 6-speed because then perhaps some parts would also swap in to other Aisin AZ-6 boxes. At the same time, it isn't like these Aisin boxes are equivalent pieces.

The 6 speed box may only require a 3/4/5 upgrade that would significantly reduce the price and difficulty of the upgrade. I have worked with MFactory gears in the past with Honda's and they engineer their products as drop in replacements unlike what Quaife was offering.

This topic has been beaten to death. Tons and tons of discussions of what appropriate gear ratios look like and what the current issues are with the current offerings. Based on your posts, you've missed a lot of that discussion. I'd suggest starting there instead.

Ive read and read and read and no one has suggested making replacement gearsets for 6 speeds from a reputable source. No one has gone beyond suggesting using transmissions as consumables.

I can see how this type of solution is not in your interest, not everyone will want to slap on a T5.

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Just saying that several of your statements in this thread are false. 3/4/5 is insufficient and there has been lots of discussion of alternate 6-speed gearsets from multiple reputable sources. If you missed those discussions, you're starting behind the 8-ball.

It's easy to sound like your right when you say nothing.

You have been here 2 years. Savington has been here for 11. These ideas have been discussed before in many threads. You are sounding like the people who would come into the studs stretching thread and spout out idea's that have been talked about years ago like we have not thought about them or tried them out.

I've read the threads on the Quaife box's, that's why I am pushing the 6 speed box. Axial load is dependent on the helix angle on the gears, reducing the angle MAY be a way to reduce this effect. I am not proposing designing anything myself, I am just attempting to get a concensus on what would be desired and asking a supplier if they would able to support the needs.

Just because I have been a member on this board for a specific amount of time has absolutely nothing to do with my experience. If you would like to be steered by someone who is out to profit from constant berating anything he doesn't sell the whole of the community will suffer.

.

I agree this is the Mecca for turbo MIATAS other platforms are running north of 1000hp in syncro boxes designed to fit inside a factory box. Again I do not pretend to know how to make this happen, just looking for a set of parameters to have a MFR work around.

https://www.speedfactoryracing.net/d...and-upper-cuff

Yes that is a very expensive example but it is designed to fit in a factory box and survives 10x the factory power level the box was originally designed to support.

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It takes an extremely talented driver and some luck to get anywhere near that on a B Honda in a light chassis. We are not comparing engines, but a factory with a turbo engine does not support much more TQ than a BP. The Honda piston ring lands typically fail before the rods.

Yes R&D is that not the goal?

Yes a 7k gear set, final drive and handcuff that supports 10x not 2x

MFacotry, if they can make a 5 speed set good for 500ish hp with better gearing. That would be better. If they cant accomplish that in a 5 speed case then 6 speed it is.

Thank You,

What specifically would you like to see different with the ratios in the each box?

i hear some complains that 1st and 2nd are too short on the 6 speed box, but not a lot of critique on the ratios on the 5speed.

Road race guys have problem with the gearing. I never make it out of second gear, and the 5 speed was perfect with that ratio for me.

First is basically useless in both the 5 and 6 speed. An overdrive option would be nice...

I do agree that the price point is going to be rough though. The issue is that from a mass production scale, it's far easier to make a kit that can use something already available and use that instead. Most turbo miatas are between 200-300 in terms of hp/tq at the rear wheels. There are so many cars out there today that are mass produced that are in that range and can take more abuse than just that on their stock gearsets. Why reinvent the wheel when it's cheaper to just use something cheaper that can be mass produced?

For the 5spd: If we only make a 3rd/4th/5th, this is very economical. It's 1st/2nd that's the expensive part to make due to having to make a new mainshaft

For the 6spd: We "may" only need to make you guys a 3rd/4th/5th, as we already have a 1st/2nd/6th for the GT86 that we made for Toyota Motorsports which, I believe, uses the same transmission. However, the ratios may be completely unsuitable, so would need to double check

The thing with the 5 speed is that they're so weak I figured you'd need to do 9310 shafts to help it hold together.

Shafts? Do you mean the mainshaft & countershaft?

It really just depends on what you guys are breaking (i.e the gears, or the shafts)

What have the gears in the GT86 stood up to? Power levels? Road race usage?

Around 500hp on our UK GT86's, Road/Race

Do you not have to upgrade the 3/4/5?

No. The gears didn't have an issue with breaking, and the ratios worked well with our 1st/2nd/6th combination

Odd. Because our 6th speeds break 4th at 300-350 ft/lbs on the track.

Performance Build Service - BRZ / FRS ? Jacks Transmissions - this provides an explanation as to potential 4th gear failure. Not Miata, but Aisin AZ-6 box from the FRS/BRZ.

Thanks Ken!

I have a spare 6 speed coming that I'm going to take some measurements on to see how close we are
to the BRZ parts that MFactory currently offers. I am also going to contact Jacks and see if they have any familiarity with our AZ-6.

If anyone has a failed gearset can you take photos? If there is some truth to what's Jacks claims the fix may not require much beyond modifying the countershaft with a stronger 4th gear clip.

@bbundy has about 20. And not all broke 4th gear.

To quote what Jack has written on ft86club:
I think this is in line with the broken tranmissions: they keep up for a while and then break 4th gear. So this is most likely due to thrust wear on 4th gear and not due to pure torque. I am interested in this upgraded 4th gear thrust washer as my 6 speed is not yet in my car.
As for gear ratios: I think the stock ratios with a 3.6:1 (which is standard for EUDM) works quite well for boosted cars.

Reply from Jacks

@bbundy Can you come in and chime in with pictures and the sorts of failures you have seen?

AZ6 clip


https://cimg9.ibsrv.net/gimg/www.mia...d28381f96f.jpg

Similar modification better explained better:

GTR Retaining Clip Modifications ? Jacks Transmissions

Interesting....Paging B Bundy, Just sent him a PM to this thread.

6 speeds mostly break 4th gear. note that an RX8 box has all the same gears in it accept 4th. and it is a strange ratio jump for 4th on the rx8, I suspect it was done for strength. I have broken multiple 4th gears and some were probably related to thrust bearing problems and one second gear in Miata 6 speeds.

I do not believe at all that the 6 speed case is inherently stronger. It has more gear pares between the bearings and more unsupported shaft length than the 5 speed. Basically only two sets of support bearings on the main shaft where the 5 speed has 3. the five speed gets away with much lighter shafts mostly because it has a stiffer case than the six speed. The six speed is stronger because the shafts are much larger and the gears have wider faces. All the weight difference between the boxes is shafts and gears I can't remember if it was 12 or 14 lb's more rotating steel bits in the six speed. That extra weight is there to make it live with a weaker case design and deal with the shaft flex.

The Quaife gear set in the five speed is not bullet proof either. I have broken the input gear, second gear, and had 5th gear seize onto the main shaft in three separate occasions.

Bob

Usually (not always though) the reason why a 6spd box is stronger is due to the closer ratio gears, so less shock load is being applied to each gear

My 5 speed dog box is supposedly rated for far more power than stock 5-speed. However it runs straight cut gears over the helical which would help stop the thrust loads. It also has a single billet input shaft / drive gear and the gears all re-arranged so it's easier to work on. Also the gearing is so close there is another entire gear between the 4th and 5th of a stock 5 speed.

The 5 speed is good because it has far nicer shifting feel and is much easier to rebuild for a novice which is a factor for the DIY miata cheapskate like me. The 6 speed adds another $2k to the total price once you factor in purchase price and that you need to send it to an expert to build.

The issue I see is there really needs to be two gear sets. A close ratio set for the track guys, and a longer street ratio set for the really high powered turbo cars and pretty much most street builds.

Helical gears are actually stronger than Straight Cut gears due to more surface contact area and spreading out the surface load between several teeth rather than just 2 teeth. The only reason why most aftermarket gear companies make straight cut gears is because it is cheaper to do so and lack the knowledge and/or equipment required to machine Helical gears. And, by playing on the fact that most consumers associate "straight cut" with "strength", they can sell them for more also, thus make even more profit. The only advantage (besides cost and ease of design/manufacturing) that straight cut gears have is less friction = less parasitic drivetrain loss. Good for WTCC and F1 cars that have the budget/sponsorships to replace their transmissions every race; not so good for the grassroots racer

In addition, although straight cut gears remove axial forces, they generate radial forces above and beyond what helical gears generate in axial forces. The larger the gear (another advantage of straight cut), the larger the radial force, and the more shaft reinforcement required to prevent the shafts from separating (this is why we use a 5th gear cuff on our 4spd drag transmissions. This removes 5th gear, which isn't required anyway, and prevents the counter and mainshaft from separating)

Another item to look into concerning helical gears with axial forces is upgraded shaft end bearings. These help tremendously in keeping the transmission intact.

First off, I think the gears should be helical not straight. If you build it straight cut there would be a far limited market. The aim here is to build an upgraded street box for a miata, that can also be used for motorsport and survive the 400+ HP cars.

Whilst I agree that a helical _can_ be stronger due to larger surface area of engagement for a given width, you tend to have wider teeth with a straight cut as they are nearly always run with dogs rather than synchros. Also the teeth themselves are generally thicker as there can be less of them so the non-hardened metal volume inside the teeth can be greater. They also have other benefits like less power loss and less loading on the case but of course the noise rules them out for anything bar track cars.

I was more commenting that the thrust load is greater with a helical gear and also the tendency for the gears to want to 'walk' apart which might be why the 5-speed boxes fail. The casing doesn't have as much rigidity as a 6-speed casing which tend to survive longer with more power. I think the gear sizing is similar so unless the gear material changed the only real difference is the layout and housing

Less loading on the case, yes, but far greater loading on the shafts forcing them to separate. But anyway, that's getting off topic. I'm more than happy to discuss the merits and negatives of both Helical and Straight Cut with anyone who is interested. Feel free to PM with any questions :)

But yes, I agree. For the street car/weekend warrior, definitely Helical cut, as not everyone wants their transmission to rattle/whine (like what it does with Straight Cut gears). BTW (not aimed at you, as you already know this), but Straight Cut gears does not automatically mean dog engagement; you can have Helical Gears with dog engagement, just as you can have Straight Cut gears with synchro engagement. As pointed out above, most aftermarket gear manufacturers don't have the available resources to make "complicated" things, so tend to go the easy route, which is straight cut gears with dog engagement. As you are down under, I'm sure you are familiar with Albins. This company has invested a lot into the proper equipment and almost exclusively make helical cut gears as opposed to straight cut (like PPG etc)

As mentioned in my post above, one of the "fixes" that we use in our own high hp transmission builds (1000whp+ Honda drag cars) is to upgrade the shaft end bearings. This helps counter any excess axial/thrust loads, and increases the life of the transmission very noticeably.

We have a very close working relationship with Jacks, so will make it a point to bring up this topic during our next discussion.

My off road transaxle uses both straight cut and helical gears. 1st and 2nd are helical, then 3 and 4 are straight. Again, I think the was due to the gear cutting process being so much less expensive on the straights. 1st and 2nd were like 500 bucks, then 3,4 were only 100 each or something. ..all sychro. My particular case has external "ears" welded in place to accommodate the force from the straight cut gears.

This is not true these boxes aren't braking because of hard shifts or anything like that. they break full throttle as the engine passes through peak torque RPM. They are braking because of torque and each time a gear tooth meshes as its rotating a cyclic load on the root of gear tooth. Up the torque and RPM and the fatigue life starts going down in a hurry weather it is shifted between gears or not. There are some arguments that heavy damped flywheels would help with peak pulse loads due to firing frequency but I think it is a small factor. The factory SR20DET that came with an AZ6 box however had a massive dual mass flywheel that had sprung travel for about 60 degrees of relative input to output rotation via two springs that ech wrap about halfway around the circumference. That might help a little.

Note that I did say "not always though" ;)

Gear teeth are in a constant mesh, regardless whether that specific gear is engaged or not. Gears don't just "break" all of a sudden; they normally wear/crack over a period of time before ultimately failing, and it is "shock" that starts this in motion

That "hard shifting" you are talking about, and it not being a cause of failure? Think of it this way, which would cause more shock:

1) A gear that has marginal load applied to it (i.e it is in a free state of rotation), then boom, all of a sudden, you have 300lb+ (or whatever you cars make) of shock load applied to it

or

2) A gear that has a consistent load applied to it

Or in laymans terms, what would cause more shock:

1) You are lying in bed, then a 300lb person suddenly lands flat on your face

or

2) You are lying in bed with a 300lb person already sitting on your face

Visual representation of axial load on helical gears

You would be very surprised at how many people on this forum would pick number 1.

Especially if it was a man.

Sorry guys, I didn't mean for this to get off-topic, and the last thing I want is to get into a heated debate on a public forum.

So yeah, back to the topic on hand :beer:

I guess in your limited time here you've not taken the time to read just about any thread. We have a serious case of ADHD :giggle:

Many of us quite literally.
Subbing for continued debate.

The teeth never have a constant load on them they have a load profile applied once per revolution going from zero to some maximum value and the load peak value is highest when in gear passing through peak torque rpm completely unrelated to when it was shifted at some engine operating point off peak torque rpm.

On a track 4th gear is a good gear for repeatedly doing asphalt dyno run with a smooth pass through the power band because on just about every track there are several straights where you get an optimal and easy shift point into 4th and have it floored flat all the way till you need to go to 5th several times a lap.

My 2 cents...

Make a gear set that is as cheap as possible for total installed cost for the end user, and is stronger than the factory 6 speed. My guess would be stronger gears for a 5 speed trans since 5 speeds are cheap and simple compared to a 6 speed. Make one ratio that is very similar to stock 5 speed gear ratio, but stronger. Perhaps make the overdrive a bit steeper, that would be a selling point to most folks who don't like spinning 4K going down the highway.

That's what quaife did. And don't do anymore. They weren't as strong as advertised, and we're expensive

Right, so just make it cheaper and stronger.

Chop-chop. What are you waiting for? :hahano:

If I recall the Quaife was/is not a drop in fitment?

It still shows as an active part on their website, is it no longer available?

Quaife didnt claim to be stronger, just different ratios. We just assumed aftermarket gears = stronger.