emilio700

iTrader: (3)

This project is not dead. Talked about the gearbox a bit with them today, while discussing some differential supply chain stuff.

Best guess right now is a one piece main shaft for greater strength. replacement cost for on dead gear goes up but it gains needed torque capacity. Primary design constraint in this project is packaging. The main and countershaft are too close together for humungo gearsets. Only modest gains possible. So we'll do whatever we can within the space available and that will be that. I know we can make useful torque capacity gains but we probably won't actually publish a number.

-slightly larger diameter gears
-slightly wider gears
-better material
-one piece countershaft with integral gears (as opposed to independent gears)

All these things in combination with a trans cooler should go a long way towards improving service life.

Nothing like prices or ETA just yet. Still many months from anything concrete.

Laur3ns

Based on feedback I got on the Quaife gears:
- Better material alone will go a very long way. Just scan a Quaife set and make one from the alloy they use in WRC. Expensive, think 4k+ for a one-off.
- Use stiff/metal motor mounts. Rubber mounts will twist the gearbox apart.

No point in going 10k+ with this as full sequential the far better option by then.

emilio700

iTrader: (3)

We're looking at closer to $3300 including steel shift forks

hf-mx5t

3300usd is also a lot of money to sink into a gearbox, if it cannot handle the power those of us with big power have. id hate to spend 3300usd plus installation / gearbox rebuild costs, only to still break a 6 speed at 450+whp / 400+ft/lb.
Id rather cut and modify the transmission tunnel to fit a box capable of even more power if i could decide on a box with decent ratios.. been looking a bit at the e46M3 gearbox as its strong, cheap and readily available here. but havent decided on anything yet. for now ive turned the power down to 400whp but wheres the fun in that

2manyhobyz

iTrader: (4)

Do you guys think this would help or BS?

Gear Work and Strengthening – Jacks Transmissions

matthewdesigns

iTrader: (8)

I'm lead tech and shop manager at Jacks. The first two methods listed on that page, as noted, do nothing in our opinion to improve the lifespan and wear of a gearset. We have seen many transmissions with these treatments and there has been no difference in the lifespan between treated and untreated gearboxes in the exact same vehicle.

REM ISF is a legitimate way to address the surface of a gear, in effect burnishing the surface and adding a very small amount of hardening in a very thin layer. This burnishing mostly helps to reduce surface friction between mating teeth, which helps to reduce trans temperatures, which extends the life of both fluid and gears.

Edit: I should add that REM ISF is going to help you extract the last few percentage points of life from a transmission. This service is primarily used by our drag racing Supra/V160 customers who are approaching the limit of that 'box. And all of our custom GT-R gearsets are micropolished by the manufacturer because allofit. This is not going to transform a stock Miata 5spd into a torque resistant super trans.

2manyhobyz

iTrader: (4)

Thanks Matt for clarifying that. I was hoping there was a solution that was overlooked.
On a slightly different note, Has anyone tried the 2005 Mitsubishi EVO MR 6-speed transmission oil in a Miata 6-speed?

-Jeff

matthewdesigns

iTrader: (8)

My pleasure.

And not that I know of. I'm using it in my 5spd, so is greddygalant, as mentioned recently in the Lube My Tranny thread. I plan on trying it in my 6spd once swapped, no reason it shouldn't be as good there as it is in the 5spd.

DeerHunter

If anyone's interested, it seems I've found the limit of my Quaife gearbox. I was at an HPDE this afternoon and, during a lapping session, heard an "uh-oh" sound from under my car. I pitted immediately and ascertained, to my relief, that it wasn't coming from the engine. There was a softer sound at idle, sort of like a bad throwout bearing, except it disappeared when the clutch was pushed in. When driving the car, it sounds like this, only more so (start at about 6:00):


Here's the kicker: Fourth gear exhibits no noise at all. Furthermore, all gears are usable and the box shows no signs of notchiness. The clutch, throwout bearing, etc. were all changed about six weeks ago and I have a couple of track days and lots of street driving on the new parts, so I doubt it was installation error. Anyone have any ideas as to where the problem lies? I fear it's going to be a tear-down, regardless, but any input will be greatly appreciated.

Laur3ns

Ok, wow. Yeah well I got massive pitting and half broken teeth after some time.

The failure mode is less harsh than the OEM box it seems, they just give up where the Quaife fades away.

I had contributing issues with the extension housing bolts breaking. I got myself (nearly) solid engine mounts. Now they still break, but slower. Replacing with 12.9 hardware in the coming days. Bottom two go first, so researching vertical flex/stress in the drive line.

Check your box for failed bolts?

k24madness

iTrader: (6)

I don't see how stiffer motor mounts can make any difference. If you feel case flex is a contributing factor then add a additional trans brace.

DeerHunter

You mean like this one? Funny you should mention it, but the shop that did my clutch found it. I thought it was a fluke.

Nagase

iTrader: (6)

Anyone have a list of the bolts needed for the extension housing in 12.9 and where to get them?

hi_im_sean

iTrader: (3)

It's been my experience that oems already use something equivalent to 12.9 for those type of fasteners. Although I have no first hand experience with miata boxes. And you should get reduced flank hardware like the one that came out or they might fail even quicker.

Leafy

iTrader: (1)

Pitting on the gear face? You need a more corrosive gear oil. Yeah that sounds weird, but yeah it works.

matthewdesigns

iTrader: (8)

Have you drained the fluid yet?

DeerHunter

I'd appreciate some of the collective wisdom here. I've pretty much resigned myself to parking the car for the season (there's only about 6-7 weeks until the snow flies in my neck of the woods) and have the winter to get it ready for next year.

OPTION A:
I could have my gearbox rebuilt, I suppose, but I'm concerned that it will just blow up again. It's lasted me about 5 years of street driving, autocrossing and the occasional track day (maybe 10 hours in total). However, since our permanent track opened up 20 minutes from my place (and I installed a roll bar), I can do 2-3 events per month. Four events in the last month did my transmission in. Some things to ponder:

• My Quaife gear set is c. 2008. I'm told that it was modified at one point for better oiling (?). Would the updates (if they indeed exist) increase longevity?
• My broken bolts indicate that the case is flexing significantly. Someone mentioned that a transmission brace might help. Anyone done this or have any idea how to do it?
• Any other case-strengthening options? Perhaps strapping?
• A transmission cooler would probably help too, although it's apparently more difficult to plumb on the 5-speed. If the housing is coming off, drilling and tapping the necessary fittings would be relatively simple, I suppose.
• Is it possible that part of the stock internals gave up the ghost and the Quaife gears are still intact?

OPTION B:
I spoke to Emilio and his uprated 6-speed internals are at least a year away, so that's not an option in the short term.

OPTION C:
Find a stock 6-speed and turn down the boost. My 4.10 Puddymod-built rear end isn't ideal for the stock ratios, however.

OPTION D:
There is talk of a T5 conversion. Sav dislikes the gearing, which is fair enough when you're racing competitively. Mine is primarily a daily-driver that is tracked for funsies, so chasing that last second is of secondary importance to reliability. Comparing speed in gears (with the same 4.10 rear-end ratio):

I'm likely to use only 3rd and 4th on my local track. Yes, there's a bigger rpm drop, but the speed per gear is similar.

Of course, this option will depend upon whether someone comes through with a bolt-in kit and whether it can work with my current differential. Other factors to consider are increased weight, less "Miata-like" shifting and whether a T5 is actually bulletproof for us high-power guys. Pros would include better highway gearing and, I assume, less noise than the Quaife produces (at highway speeds, gear noise drowned out tire sizzle and wind roar).

Any and all input will be most appreciated.

No, I haven't had the heart to do anything with it yet. I'm assuming I'll find chunks of metal.

Leafy

iTrader: (1)

At the very least you'd want the .8 5th gear for the t5.

TurboTim

iTrader: (9)

Yep. While the .63 is nice on the highway, it's a huge unnatural drop in rpms.

I'm not sure whatever happened to this supposed kit:
MX-5 Miata Forum - View Single Post - A question regarding interest

DeerHunter

Fair point. Some Googling shows that there's a 0.73 5th gear available. Can you pretty much mix 'n match when building a T5 tranny? That might be a good compromise ratio.