Is there a stonger 5 speed to look for? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-12-2010, 11:57 PM   #21
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Why isn't anybody looking at the regular non-turbo second gen RX7 tranny? Are they weak? I know they are very plentiful and cheap.

I brought the horse. Let's beat the ******!
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Old 05-12-2010, 11:58 PM   #22
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Why isn't anybody looking at the regular non-turbo second gen RX7 tranny? Are they weak? I know they are very plentiful and cheap.
Don't they have the same fitment issues?
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Old 05-13-2010, 12:02 AM   #23
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Don't they have the same fitment issues?
Should, though I think there are some case differences, not sure if it's more than just casting differences. Which brings up the question again, why isn't someone filling this need with a swap kit. Isn't it just a plate, a few bolts, a weld in or bolt in mount and maybe some simple wiring (if that).
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Old 05-13-2010, 12:07 AM   #24
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People are not making swap kits cause its not profitable to do so. How many people do you HONESTLY think will buy one like, today.
Not as many as it seems.
You want more power on miata stock 5 speed is fine. You want LOTS more the 6 speed is fine.

You want LOTS of power and PERFECT gearing you shell out the dough for a dogbox.

OR

You just swap in a v8 and have the power+torque+gearing all in one
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Old 05-13-2010, 12:10 AM   #25
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You just swap in a v8 and have the power+torque+gearing all in one
SHHH. That's like waving crack in a recovering crack head's face. I'm trying to talk myself back into a turbo.

I've seen a lot of Miata parts that I have thought "no way they sell more than 1 a week" and yet they produce them. I bet they would sell enough to make it worth it, especially considering they would be THE only one making them that I know of.
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Old 05-13-2010, 01:53 AM   #26
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OK let's talk about the 84 & 85 RX-7 GSL-SE 5 speed transmission. I heard it's not really any stronger, but it certainly has different gear ratios. I was reading from an older thread that you need to swap the rear tail section and the bell housing onto it, but that's not too major. I'm still sort of a gear ratio newb, and not sure how it would affect the car. I'm looking for something that will be geared better for drag racing. Here's the comparison of gear ratios for the RX-7 and Miata 5 speed

RX7 (1st, 2nd, 3rd, 4th, 5th)
3.622 2.186 1.419 1.00 .807
Miata
3.13 1.833 1.303 1.00 .814

It's interesting how it gets shorter in 5th, but much longer in 1st, 2nd, and 3rd.

edit - I just found someone locally selling a 1985 gsl transmission for $75. I might pick it up tomorrow.
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Old 05-15-2010, 12:45 AM   #27
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Coming from an rx7 guy here

T2 trannies are very cheap around $150-200 from an importer But the miata never had that series of tranny, it shares alot in common with the 89 and up B2600 trans

Rx7 N/a FC trans is the same family as the miata trans so you could do some parts swapping and get one into your car But, if you have a 1.6l piston motor you wont be making nearly enough torque to take advantage of the Longer gears (my second gear goes to 110km/[email protected] rpm)

As putting a T2 trans in you would need a Custom bellhousing,flywheel and Drive shaft then its the mount...

N/a trans in Rx7's usually let go about 300ish hp I put a T2 motor in my FC with the n/a trans, its making some wierd noises now lol


the N/a circuit guys that Do run the N/a trans usually take Miata 1,2,3 FC 4th and b2200 5th gears

Personnaly I think that if i had a miata and wanted to make power (over 300whp) I'D tear a spare trans down get the gears cryo treated new bearings and use a good quality lube in it

Oh and Dustinb that GSL Prolly came off the back of a 12A motor and wouldnt have anything in common with the miata trans as far as i know
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Old 05-15-2010, 01:29 AM   #28
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Well I am currently running an NA rx7 transmission in my Miata.

First, it isn't a complete bolt up swap. There is some massage worked need, and it needed on the inside of the casing. Once the bellhousing and tailhousing are swapped, it looks like a standard miata from the outside. I think I have about 6 hours of work in my transmission swap, and about 3 of those were just in figuring out how to take apart the transmission.

Currently I am not making enough power to test the limits of the rx7 transmission yet. but i can make a few comments.

1) the n/a rx7 does have a random issue were a few 2nd gear synco starts to go. My does it and it shifts fine, but just feel rougher going from 1st to 2nd.

2) have had the 1.6L N/A with the rx7 5-speed and a 4:30. I will say that lack of torque in 1st was mildly noticeable, but didn't ruin the car. It was amazing on the hwy, but it didn't have much pull in 5th gear below 4k(which was around 90+ mph)

3) currently I am running 1.8L turbo with massive problems. I also swapped to a 4:10. The rx7 and 4:10 are great on the hwy. With the turbo, when it was running right-er it pulled nice off the line.
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Old 05-15-2010, 02:49 AM   #29
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Ok I'm confused.

The NA rx-7 transmissions are weak. At least as weak as the miata transmission if not weaker. Some 1st gen guys have debated using a miata trans as a swap, that should tell you something. The GSL-SE is stronger than a NA FC transmission, but not hugely so. Mine has held up to civil 250whp driving for awhile, but 2nd gear cannot take hard shifts anymore.

A TII swap may be worthwhile as they are extremely cheap and very stout (400whp=A-OK), but rotaryman is scaring me talking about the gearing on the rx-7 trans. It is much, much shorter through the 1st three gears, look at the gearing already posted. some of you complain about the stock miata gearing, rx-7s are shorter but many can rev out to 8k, so it's not as much of an issue.

Also the TII and the NA swap are a DIRECT BOLT IN swap between each other, so if you can fit one, you can fit the other, minus clutch and flywheel issues (turbo's is bigger). I have no idea what "series" you are talking about. The only external difference between the NA and TII rx-7 transmissions is ribbing on the casing of the TII's.

And a GSL-SE never had a 12A in it, and NO RX-7 transmissions have anything in common with a miata transmission.
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Old 05-15-2010, 07:52 PM   #30
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Ok I'm confused.

The NA rx-7 transmissions are weak. At least as weak as the miata transmission if not weaker. Some 1st gen guys have debated using a miata trans as a swap, that should tell you something. The GSL-SE is stronger than a NA FC transmission, but not hugely so. Mine has held up to civil 250whp driving for awhile, but 2nd gear cannot take hard shifts anymore.

A TII swap may be worthwhile as they are extremely cheap and very stout (400whp=A-OK), but rotaryman is scaring me talking about the gearing on the rx-7 trans. It is much, much shorter through the 1st three gears, look at the gearing already posted. some of you complain about the stock miata gearing, rx-7s are shorter but many can rev out to 8k, so it's not as much of an issue.

Also the TII and the NA swap are a DIRECT BOLT IN swap between each other, so if you can fit one, you can fit the other, minus clutch and flywheel issues (turbo's is bigger). I have no idea what "series" you are talking about. The only external difference between the NA and TII rx-7 transmissions is ribbing on the casing of the TII's.

And a GSL-SE never had a 12A in it, and NO RX-7 transmissions have anything in common with a miata transmission.
the only reason i'd see a first gen guy to try a miata box would be for the gear ratios

There are transmission families in mazda what i mean by that is the gear box (not the bellhousing or the tailshaft) are the same

Just like honda has The B,h,k,f, j series motors

the gearbox between the RX7 na, miata and B2200 share 99% of the major components in the gear box

the Turbo2 trans shares 99% of its components with a B2600

As far as the T2 trans and the Na FC trans go they are Nothing alike, starter,clutch, flywheel, driveshaft, gearing, clutch slave are All different the only 3 common points on them are that it'll bolt to a 13b, the trans mount and the shifter location

Some info
http://www.rx7club.com/showthread.php?t=524587

personally the amount of money you would be spending to try to put a t2 trans in just wouldn't be worth it
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Old 05-16-2010, 01:13 AM   #31
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If you're making the type of power that needs a TII box, that should be small potatoes. Custom driveshaft (200-300, or mod that stocker for less), you need a clutch anyway, BAM.

starter is 15 bucks, clutch slave is 50 new, street price is less. Bolts up the same. So you can get a tranny that'll take 500hp for less than 1000 installed, or pay for an adapter (the only hardpart of the swap) for a tranny that is the same as stock with worse gearing? Knock yourself out with the NA trans.
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Old 05-16-2010, 01:35 AM   #32
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No.. just No

it won't be small potatos

You Will need an adaptor kit of some sort for the bell housing because a T2 trans will not bolt up to a miata motor

Most adaptor kits (even for Honda's H-series motor to a D-series tranny go for well over 1k Alone

So parts:
T2 trans $150-250
Clutch $350-500 (you are making enough power to use it i assume)
Driveshaft $2-300
Starter $20
Clutch slave $30
Adaptor plate+custom flywheel 1K easily unless you are a machinist and can do it yourself even then the hunks of aluminum would be around $400 for it

Then a tranny mount ??

and the fact no one has done it so its not even known if the shifter will come up in the right spot...

If you are going though all that trouble you may as well just get a T56 tranny or a getrag out of something


If you knew what goes into fabricating anything you wouldn't be saying thats the only hardpart
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Old 05-16-2010, 04:03 AM   #33
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Originally Posted by Rotaryman View Post
If you knew what goes into fabricating anything you wouldn't be saying thats the only hardpart
LMAO, ok dude. I'm gonna let this go, but if you think that kind of cash is alot for a 400hp car, you haven't owned many 400hp cars. You can fab adapters for less, and your other options for a tranny that'll take the power are $4000+ dog boxes. The adapter IS the hard part, shortening tail-shafts is easy.

This thread is about stronger tranny's, the miata already has the better gearing. Sure you can put gears in a box, but it won't stand up to abuse, if you want that, get your fab skills I know nothing about and make an adapter.
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Old 05-16-2010, 04:30 AM   #34
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Cool thread.
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Old 05-16-2010, 01:26 PM   #35
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Sorry im not trying to fight with you here

the point im trying to get across here is that it would be easier and cheaper to put a 6 speed box in rather than being experimental with the T2 tranny ya it can handle a Ton of power but how much power do you want in a 2100lbs car

And ya I have no clue what it takes to build a 400whp car let alone a Rotary 400 hp car.....
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Old 05-16-2010, 07:28 PM   #36
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Originally Posted by Rotaryman View Post
Sorry im not trying to fight with you here

the point im trying to get across here is that it would be easier and cheaper to put a 6 speed box in rather than being experimental with the T2 tranny ya it can handle a Ton of power but how much power do you want in a 2100lbs car
Hey there we go, I agree with that 100%

I think the TII tranny may be stronger than the 6-speed, but it's still pain in the ***. I was just saying since people were asking. IF you look at rx-7 trannies, the TII is the only one worth looking at that, but even that is... bleh.

The moral of the story: stick with miata transmissions. I have an FB with a TII swapped, and a garage full of spare TII's, but I wouldn't want to drop it in a miata, too much work when the 6-speed is a really great swap. The 5% of miata drivers that need more than the 6-speed know what they need.
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Old 05-17-2010, 01:37 AM   #37
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Yup! exactly not worht the headache

Call me a ricer but id love a 6 speed rx8 tranny in my car.. even tho i know nothing lines up besides the motor lol
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