I would be interested in any guidance available concerning alternate transmissions, bellhousings and the like that will bolt into a 1st gen rx-7.

Thanks!!

 

I have a Mandeville modified Leeson trans that is need of some small repairs that will be for sale. this is a crash box(similair to a dop ring) can be shifted without using the clutch. mandeville still sell this trans for about $7000 last time I checked. there are bellhousings out there that will allow you to use any of the full race transmissions,jerico, Liberty, Saenz, Hewland, Quaife as well as a T5 or T56. I believe there are also some adapters for Toyota Supra trans as well. Mazda Comp has the PBS dog ring drop gear trans as well. All big buck though. what are you looking for?

 

Thanks for the quick and wide ranging response Tim! I really should have given more info. I am currently developing a 1st gen EP roadrace car, but I have also built it with the possibility of using it in endurance races. I have been using up my old "$100" stock trannies at a phenomenal rate, and I knew they would not be a good solution for my increased horsepower in the long run. They aren't great ratios for performance, and they certainly are not 100 bucks anymore as they are getting harder to find. I'm researching Miata gearsets, and alternate transmissions for roadracing, including those legal for EP, GT3, and Endurance. I'm interested in any knowledge I can get!

 

For EP I think you can use any trans that is not sequentially shifted. GT and all others are open as well. The miata set is a good IT type setup, but for EP you should use something better. Budget will be your problem.

 

The smooth case RX-7 tranny with the Miata gear set is an excellent choice in EP, especially if your not looking to win the run-offs. It's very durable and its performance is more than adequate to be competetive in EP. It will also save you a weight penalty. You should seriously consider this option. The real drawback is really need to run a high diff-gear (4.88 / 5.1) to make this combo work optimal...

The money real drives this:

RX-7 tranny w/ Miata gear set: $800-$1000

most dog-boxes: $5k +


-Bern

 

could you be more specific "smooth case" year ,model , generation?

 

1st/2nd gen 13B NA tranny

-Bern

 

Thanks , Bern

 

I have heard that there are bellhousing adapters for a T-5 to a rotary. The T-5 can be built to do about anything and might be a decent compromise in terms of cost between the two options outlined above.

 

Road racing rotaries must have very close ratios if you want to run fast. This means a very tall 1st gear, very low 5th gear so that all gears are useable. The cheaper alternatives listed above have wide ratios and will have slower lap times since the street ported EP motor will drop to low rpms (and low torque) every time you shift gears. Transmissions from street cars usually end up being just two speed transmissions, because only 3rd and 4th gears have useable ratios.
In the early and mid '90s when I was running a street port EP 12A motor, I was amazed at how going to a Mazda Factory road racing close ratio tranny instantly dropped my lap times. I have one for sale, a genuine Mazda Factory Road Racing Transmission, with larger input shaft, roller bearing output shaft bearings (instead of the bronze bushing,) 2.2 1st gear and 0.88 5th gear ratios. First gear is usually just to get you rolling, and then you have four useable gears for racing, second thru fifth. I wouldn't use 1st gear even in the really tight turns because I would get wheelspin coming out of the turn. This first gear is like second gear in a street car transmission. This is a true bolt in transmission for 1st gen RX-7, no mods required. This transmission is in good condition, and it is perfect for E-Production racing. I will sell for $2500 plus shipping. Special racing shifter is included. Email me at speedturn@hotmail.com, please put "Racing Transmission" in the subject line.

 

Great info - thank you! speedturn - I would buy that in a second if I had the immediate budget, and I thought it wouldn't break immediately. There are a couple guys running Mazda Comp boxes arouind here, and they seem to break constantly. This is on a GT2 PP 12a, but still. Tell me more about it if you don't mind - how sturdy is it?

And Bern - can you give me more info on who might be able to accomplish a Miata/Smoothcase if I decide to go that way?

Thanks all

 

Boswoj, any competent tranny shop should be able to set it up for you. The Miata gear set is a direct fit for the RX-7 tranny. It's just like a tranny rebuild. You just need to source the gear sets through MazdaSpeed Motorsports (Mazda Comp) and have them installed.

If you'd like to speak to a Rotary specialist that runs EP, you can contact Mazdatrix, as they've run this box in both 1st and 2nd gen EP's.


-Bern

 

anyone with $2500 should buy that trans from Speedturn. That is a great deal and would be an asset to any race car in any class. I would sell my Leeson for about half that, but it does need a couple parts to be race ready.

 

I was under the impression that the input had to be cut down 1/2" or so to work correctly. Bad info?

 

yep, or put an s5 fc input shaft in there

 

The S5 input is interchangeable? Felix Miata's chart shows the Miata 5-speed having a 21-tooth gear on the input shaft, while all "fine pitch" ('83-up RX-7) have a 22 tooth.

No listing for '99-up 5-speed, but the gear ratios are the same as earlier Miata units.

 

we did the swap the other way, the miata guys want the fc gears. the miata input shaft went right onto the fc trans guts and into the miata case.

we've got an rx8 6 speed apart in the shop right now, shafts are beefy!

 

The splines on the miata and RWD 626 input shaft need to be ground back 1/2". So the tip of the input shaft maintains the same shape as rx7 input shaft. If that's not done, the trans will sporadically pop outta gear while driving. We just gave the 626 and rx7 input shafts to a machine shop and said 'make this look like this'. Fifty bucks.

I have had 2 626 boxes made and the length of it's input shaft is 1/16" longer than 1st gen rx7. We did not cut the length down, there is enough room in the rear of the e-shaft to accomodate the minute extra length.

Never measured the miata length.

To answer the original question, mazdacomp sells a very nice miata gearset and input/output shafts with true close ratio gears. It ain't cheap, but is cheaper than aftermarket and it is stronger than stock and uses other miata internals which are easy to source and racer priced. Just search their site under miata and trans for more info.

 

On my earlier post, I had the ratios incorrect on my earlier post for my Mazda Factory road racing close ratio tranny for sale. Here are the correct ratios:

2.350 first, 1.608 second, 1.240 third, 1.00 fourth, .888 fifth

These were the gear boxes used for the peripheral port IMSA GTU cars throughout the '80s; the trannys that made so many Daytona 24 hour endurance race wins. They will hold up to road racing, but not to drag racing. I have the Mazda parts sheets with part numbers.

Mazda now offers these gears thru these part numbers:

0000-02-9701 C GEARSET, COMPETITION - EMCO 12A, 13B 1981-2003 $2,996.00

Notes: Competition gearset for all Miata or 1981-92 RX-7 smooth case transmissions. Gears are stronger than stock. Ratios: 1st-2.35:1, 2nd-1.55:1, 3rd-1.240:1, 4th-1:1, 5th-.881:1 Requires input shaft for either RX-7 or Miata, sold separately.

RX-7 Input Shaft 0000-02-9700-RX, INPUT SHAFT, COMPETITION - EMCO 1 RX7 12A, 13B 1981-92 $616.00

So it would cost you $3600 to buy these gears, and then you would still have to buy all the bearings, shift linkages, cases, etc, and pay to get the bearings pressed on and get everything set up to work, so you would end up with quite a bit (probably $4500) invested to go that route. A Saenz tranny goes for about $4500 as well.

Mine is a bargain at $2500. There is about 6 hours road racing time since it was last rebuilt with new bearings and synchros.

Speedturn@hotmail.com

 

If you use the FB tail shaft you can use any N/A FC tranny. Also the RWD 626 tranny will bolt in with the FB bell housing and tail shaft. I heard the same thing about Miata thing, but i don't know for sure...

 

Not according to this:

http://mrmazda.no-ip.com/tranchrt.txt

 

I dont know about FC but a few years ago I installed a FB tranny with miata internals on a RX-2. The builder shortened the input shaft. Pix are below.

 

More info for anyone else interested:

5th gear interchange chart: http://members.aol.com/solomiata/Mia...terchange.html
SoloMiata drivetrain interchange guide: http://members.aol.com/solomiata/Drivetrain.html
Regearing Mazda transmissions: http://www.angelfire.com/darkside/de...nsmission.html
Miata VS RX-7 input shaft comparison: http://myweb.cableone.net/currie/tom/RX7/trans.html

 

Great info. I'll bet the cheater spec Miata cars are using the RX-7 5th gears to get a good close ratio 4th to 5th shift.

 

Within .001 is the same as identical. You're not going to get .001 difference without *very* *very* fine teeth.