Drivetrain
Contents
Solo Rules
Drivetrain is virtually unrestricted.
Transmission
Ordered a quaife wide gearset from Autotech, which is being sent directly to Advanced Autosports, who will rebuild a 94-97 tranny using these gears and send it to me. Should be all done by mid january, ideally.
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. Has anyone explored shot-peening/cryoing stock sets?
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: 2.35, 1.55, 1.24, 1.0, 0.881 (Identical to the Quaife Close Ratios)
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.
I'm trying to contact several people to see about the mythical 3.3 ratio, and might end up being able to make one custom. This would be a great combo with the 6-speed.
Ratios
3.760, 2.269, 1.645, 1.257, 1.000, 0.843
Anyone ever make alternate gear ratios? Possible to change?
Cost/Availability
Seems to be around $700. Somewhat rare.
Speed Options
- (nothing lower than 3.636 seems to exist)
- 3.636: 38/62/86mph
- 4.3: 32/53/73mph (this one seems the likely choice, and also the easy ratio)
- 4.1: 33/55/76mph
TRE Box
There seems to be a guy who makes custom Miata transmissions. Taylor Racing Elite? The Springfield Dyno page references it, and it might be interesting to explore...
Jerico
Jerico also makes custom transmissions. Mckee's running one. Maybe get something like their 3 speed?
Fluid
What fluid to run? Redline?
Starter
The later Miatas had a (3? 4?) pound lighter starter that is, in theory, a direct swap.
Driveshaft
The 99 carrier swap will bring a new slightly shorter driveshaft. The stock one is 11 lbs, the MSM shaft is 14 lbs. At some point someone made a CF driveshaft at about 8 lbs, but it's not available anywhere that I can find. Probably not worth it to bother. :)
Rear End
The car currently has the stock 1.6 rear end in it. No idea yet if it's a VLSD or open. I need to locate a new 1.8 pumpkin + axles to swap to.
Available Ratios
- 4.888 -- Mazdaspeed Motorsports has a kit (and I have one)
- 4.44 -- Mazdaspeed part # M054-27-110A, 491$
- 4.3 -- 99+ (I have one of these too)
- 4.1 -- 94-97
- 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
I have the OS Giken with the high power option sitting on the shelf waiting to go into a diff.
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$. Yoink.
Axles
Stock miata axles with the 99 carrier swap hold up to a lot of power. ABS Rings part # is BC4C-33-471. ~34$ each.
