Drivetrain
Solo Rules
Drivetrain is virtually unrestricted.
Transmission
The transmission is a 94-97 trans core, fully rebuilt, and using the Quaife wide ratio gearset (bought from Autotech, installed by Advanced Autosports).
5 Speed
The stock Miata 5-speed transmission has been shown to have issues with remotely high power levels in stock form. They're cheap as hell, though. AA has a rebuild parts list to do rebuilds yourself.
Stock Ratios
3.136, 1.888, 1.330, 1.000, 0.814
Quaife Gearset
There is a gearset by Quaife available, usually 4-6 weeks out. Wholesale price is about 2500$ shipped, so it'll be more in stores, and there's two ratio options.
Ratios:
- Option 1: 2.564, 1.670, 1.273, 1.000, 0.794
- Option 2: 2.350, 1.550, 1.240, 1.000, 0.881
OS Giken Gearsets
OS Giken apparently used to make a 3-speed gearset, but it's discontinued and everyone's OOS everywhere.
Ratios: 2.604, 1.639, 1.228
EMCO Gearset
More info at this post. Costs 3300$ for the gears + input shaft through Mazdaspeed right now. Ratios are identical to the Quaife Close set.
Speed Options
(Assuming 8000 rpm redline)
Stock:
- 3.909: 45/74mph
- 4.1: 43/71mph
Quaife Wide:
- 4.3: 50/76mph
- 4.44: 48/74mph (this gearset gives a much less annoying 5th gear too)
- 4.625: 46/71mph
Quaife Close/EMCO:
- 4.44: 52/80mph
- 4.625: 50/76mph
- 4.888: 48/72mph (almost 4000 rpms @ 60mph)
OS Giken Miata Ratios:
- 4.44: 47/75
- 4.625: 45/72
- 4.888: 43/68
6 Speed
Some of the later Miatas had an option for a 6-speed, which is an entirely different design, and holds up to quite a bit more power. Not bulletproof, but a lot better.
Stock Ratios
3.760, 2.269, 1.645, 1.257, 1.000, 0.843
Cost/Availability
Seems to be around $700. Somewhat rare.
Speed Options
- (nothing lower than 3.636 seems to exist -- the 3.3 "NZ Kia Sportage Front Diff Ratio" seems to be a unicorn)
- 3.636: 38/62/86mph
- 4.1: 33/55/76mph
- 4.3: 32/53/73mph (this one seems the likely choice, and also the easy ratio)
TRE Box
There seems to be a guy who makes custom Miata transmissions. Taylor Racing Elite? The Springfield Dyno page references it, and it might be interesting to explore...
Jerico
Jerico also makes custom transmissions. Mckee's running one. Maybe get something like their 3 speed?
Fluid
Currently using Royal Purple 75W-90.
Starter
Using a stock 99 starter. 6.0 lbs instead of 9.8 lbs for the NA manual starter.
Driveshaft
Using a 1.8 (shorter) stock driveshaft. The stock one is 11 lbs, the MSM shaft is 14 lbs. At some point someone made a CF driveshaft at about 8 lbs, but it's not available anywhere that I can find. Probably not worth it to bother...
Rear End
Using a 1.8 rear end conversion with the OS Giken hi-po option in it from 949. Starting with a 4.3 R/P for now, and we'll see if I need to go to a 4.44 if we never end up running out of 4.3 gears.
Available Ratios
- 4.888 -- Mazdaspeed Motorsports has a kit (and I have one)
- 4.625 - In theory available in the NZ Kia Sportage 4x4 front diff, but it's basically a unicorn set...
- 4.44 -- Mazdaspeed part # M054-27-110A, 491$
- 4.3 -- 99+ (I have one of these too), really common
- 4.1 -- 94-97 5-speed
- 3.909 -- US 6-speed
- 3.636 -- Australian 6-speed (!? where do we get one of these)
In theory there's other options, but they may require some tweaking. See this Diff Info link for more options/info.
Differential Options
Torsen
Works great, holds up to a lot of power, cheap and available.
OS Giken
949 Racing worked with Bob Bundy on a high power option for the OS Giken diff. It's now available at 949 for 1734$.
Axles
Stock miata axles with the 99 carrier swap hold up to a lot of power. ABS Rings part # is BC4C-33-471. ~34$ each.
