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Miata Gears in NA transmission

Old 07-12-02, 04:59 AM
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Miata Gears in NA transmission

Who is running the Miata gearset in their transmissions? Any bitches, complaints, downside?
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Old 07-15-02, 10:22 AM
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No, but I can't wait to hear how they turn out, how much did it cost from pinapple racing?
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Old 07-15-02, 10:53 AM
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Why not just get a Miata transmission and swap an RX-7 front housing on it?
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Old 07-15-02, 11:41 AM
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Also performing a total rebuild at the same time. Doing some other stuff inside as well. The front cover swap sound good. Who has done it?
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Old 07-15-02, 01:01 PM
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what's the advantage of this? Are we talking 5spd or 6spd Miata?
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Old 07-15-02, 01:17 PM
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5 speed. Closer ratio gears for auto-x, along with the 4.30 rear-end
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Old 07-15-02, 01:18 PM
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there's a 6 speed miata?
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Old 07-15-02, 01:39 PM
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yeah there is a six speed miata.
the earlier miata trannies (5speed) could bold up to the rx7 but the 6speed ones dont
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Old 07-15-02, 01:52 PM
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The Miata gears are almost as good as the RWD 626 gears. Miata trannies are everywhere but 626 trannies are a bit hard to come by, especially as most of the ones that haven't turned to metallic fertilizer have had their trannies harvested for use in RX-7s.
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Old 07-15-02, 04:55 PM
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you arent "supposed" to swap just the front cover, because everything but the tailshaft housing is line bored as a set, that and you have to swap input shafts. one is longer than the other

mike
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Old 07-15-02, 10:10 PM
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Originally posted by banzaitoyota
5 speed. Closer ratio gears for auto-x, along with the 4.30 rear-end
What class are you going to run that setup in? I'm 99% sure that isnt' SP legal..

PaulC
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Old 07-15-02, 10:32 PM
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You are right Silkworm, its most likely not legal.I really don't care what class the Sports Car Communists of America decree I must run in. I just enjoy driving a car the way I want to set it up, at it's limits.

If they stick me in AM it doesn't matter, I just enjoy driving.
I've had this particuliar beef with the SCCA for 20+ years now, ever since I wanted to run my 2TG toyota.
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Old 07-16-02, 01:24 AM
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Gotcha
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Old 08-07-02, 01:21 AM
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I know a 13b peripheral port that had a miata 5 speed in a rx7 case and it was a cheap way to get semi-close ratio gearing. Peejay, not sure if a rx7 front cover would fit a miata case but it would fit a 626 case; but the shift lever location is further forward on the 626 case, perfect for 79=80 rx7 but too far forward for 81-85. Plus you need to use the long *** 626 shift lever with long throws

Miata or 626 transmissions are not IT legal for Rx7s. This would bump you to EP with weight penalty (50lbs I think). Or GT-2/3.

I know a 1st gen GT-3 with 12a bp 246hp at the flywheel that used a 626 trans for 2.5 years with NO TROUBLE.

I have 626 guts in my 1st gen 81-85 style case and it kicks butt. I will be doing NASA HPDE in los angeles this year and race TCRA 2.2l challenge next year.

Here is a writeup I did awhile ago.

How to install the guts of a 79-82 RWD 626 tranny into a
81-85 Rx-7 case

From the 626:

Forks (not really, see below)
Anything not mentioned below

From the Rx-7:

Shift Rods
Shift lever & ****
81-85 transmission case and bellhousing

626 or Rx-7 Bearings

Might need the 626 center bearing plate, some people say they need it, other's don't.

Mazdacomp and others say the splines 626 input shaft is too long, and needs to be machined down to the same length as the Rx-7 shaft. Approximately 1/2", but measure to be sure. You are machining the splines back only, you are not shortening the input shaft. The input shaft is 1/16" shorter on the 626. That's okay, it just won't fit quite so far into the pilot bearing.

Because the 79-82 RWD 626 and 79-80 Rx-7 both use the long shift lever that's positioned further forward in the car, if you have a 79-80 Rx-7, all you need to do is slap a 79-80 Rx-7 bellhousing onto the 626 transmission, grind back the input shaft splines, and you're ready to go.

I had a problem with my third gear. It jammed stuck in 3rd gear and did not want to come out. On further inspection we found that there must have been something in the 626 case that allowed the 3rd gear shift rod not to slide back all the way. The rx7 case had no such thing (it was fixed mechanically elsewhere in the tranny). So we lathed a groove on the 3rd gear shift rod and put an e-clip on there so the e-clip would bump into the center section of the case, thus preventing shift rod from sliding back too far and jamming.

And we found out that the shift forks from a 1st gen rx7 were exactly the same as the 626. We replaced two 626 forks with rx7 ones.

Gear ratio's on the 626 tranny:
3.214 1.818 1.296 1.000 0.860



I got this off Mazspeed.com awhile ago:

626 box to 1st gen only conversion.
You need from your rx7 box:
* bellhousing / case.
* clutch pivot.
* tail housing.
* selector rods.
* gear stick.
Modifications:
You need to taper the front of the input shaft approx 7mm back further than it already is. Measure from the front face of the 7 box to the back edge of the taper before you pull it apart then transcribe this measurement when the 626 guts are put into the housing.I marked mine with masking tape and ground it back using a 4" angle grinder. A bit ruff but it did the job.
The rx7 tail housing and selector shafts are needed to get the gearstick in the right place.
I think I had a problem with one of the selector falks hitting on the tail housing which with a little attention from the affore mentioned grinder, fixed the problem but be careful in regards to the reverse light activation parts on the selector. My reverse lights come on for 5th gear as well as reverse so I disconnected the light. It would be best if you could get this working properly while the box is out of the car maybe using a multimeter to see when the switch is being activated.
I have run this box for about 8 sprint meetings now as well as my daily driver with a 200 hp 13b with no trouble.I previously asked the question of relyability on this site and got favourable responces.
In aus rx7 boxes are $450, 626 boxes are $220.
Good luck.
tony.

Best of luck!
-bp-
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Old 08-07-02, 06:03 AM
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Drivefast, thanks for the info. My box is out at Rob golden's shop right now being done. John
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Old 08-08-02, 10:50 AM
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Originally posted by DriveFast7
but the shift lever location is further forward on the 626 case, perfect for 79=80 rx7 but too far forward for 81-85. Plus you need to use the long *** 626 shift lever with long throws
You say that as if it's a BAD thing. I find the SA shifter is easier to reach since it's much higher up (right next to steering wheel) and the pivot placement seems more natural.

I found that an engine dowel pin has the same threads as the shift lever in my '85. I now have a 12A dowel pin for a shift ****. I like it SO much better than the factory stub-stick feel. I'm still debating on whether I should drill out an old shift **** so it slides on over the dowel pin, or leave it as-is. I kinda like it as-is, though...
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Old 08-17-02, 08:17 PM
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Thanks for the 12a dowel pin shift **** trick Peejay. I might try that.

As far as the long SA shift lever goes, to each their own. I like the shorty 81-85 style. Short throw snick-snick action.

-bp-
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Old 10-28-05, 08:31 PM
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I've done the miata gear change into an RX-7 case and you have to use the complete RX-7 case except for the center bearing carrier and have the input shaft machined to match the length of the RX-7 input shaft. If your in the Vancouver/Portland area I can do this modification for you. The swap works great with no problems.
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Old 11-05-05, 10:23 PM
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This is great info. I don't mean to hijack, but does anyone have the Miata ratios handy?

I need to buy / build a trans for my EP car, and have only been looking at 626 boxes. Miata gears would be a great alternative.
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Old 11-07-05, 04:42 PM
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