Close-ratio Transmission?
 

Hey guys, I've been searching around and can't seem to find anything, even on the forums, I've been trying to find a close-ratio transmission. I've been on RB and Mazdarotaryparts, and they don't seem to have anything. If not a close-ratio tranny, are there at least interchangeable rear-ends that have different final drive ratios?

I've found a dog box transmission online before, is that the only choice?

I was looking into a GM muncie before the m22 model has very close ratios, but I don't know how well it would fit in thetrans tunnel tho

search os giken close ration gear set on google. you will come up with one for the fd and the fc, there not cheap though around $3600 for the kit plus you need some new bearings to replace the gear set. i have heard the track guys swear by them. good for consistent high rpm driving.

how much power? the rx8 trans is great for n/a, although i'm not sure how it stacks up in the close ratio department, feels great, and low rpm drop between gears, but they are 6 speeds... as i recall the 6th is higher then the 5speed rx7s 5th. and there is an extra gear between 2/3.... so 1-4 covers the same range(0-~105mph) as the rx7's 1-3. then rx8 5th is the same as rx7 4th (1:1), then the rx8 has a 6th simular to Fb's 5th gear.

they also handle 9k rpms without much fuss, and can be had for $400-700. the power limit is around 200-250 ft lbs. but it all depends on how you drive.

I have a RX8 Trans, flywheel, clutch, starter, and throw out bearing. The Trans it's the same length as the TII and the TII driveshaft fits. You'd need a new crossmember made and some way to move the shifter back about 3.5". Otherwise, it looks like a pretty easy swap. My trans needs a shift fork, but this is a common problem with the 04-08 Trans'. Less than 100k too. If you're interested, pm me and I'll make you a good deal :)

The RX-8 trans is like having a close ratio 4-speed (2.2-ish 1st, 1.0 4th) with an overdrive on one end and a granny gear on the other.

On the other hand, for some people, a 2.2-1.0 spread is wide. I've seen five-speed boxes with 1.9 1st and 1.1 5th.


Barring that, Giken makes a gearset and so do Quaife. Barring THAT, most roadrace transmission companies make transmissions that mate to rotaries or bellhousings for same, but if $4k for a gearkit is expensive, you probably don't want to spend $20-50k for a whole transmission.

I know bellhousings that mate to standard GM trans pattern exist, which would let you use basically any drag-specific transmission ever made (Liberty, Jerico, etc.) as well as circle track units. IMO most of these transmissions shift like crap and the shifters available kinda suck if you like to downshift.

Have you been on Mazdatrix's website? They have parts for the rear differential that you should take a look: 86-95 Ring & Pinions, Bearings, and Seals

Also, you should look up the miata tranny swap.

or like the competition boxes from the 80's with a granny gear 1st...

I used to have excellent results with PAR gearset from Australia on my GTR.
Now I will use on my road race FD3S

Is there a site that will tell me the ratios of all the FC transmissions? :/ I just bought an '88 GXL shell, but it has a tranny, would my '90 GTU have a shorter ratio? I know it's S4-S5, but all I'd need is the keep the S5 flywheel right? Hahaha at least rotary resurrection seems to say so

Mazdatrix has a list: Flywheels

Haha, that's perfect, thanks a lot man

You could try WPS Racing | Rotary Performance send them a email. I know they have flywheels and close ratio gearboxes on the selve. But they are in Australia.
Cheers

I wouldnt call the rx8 6 speed close ratio.. 3rd to 4th is huge gap, especially for NA engine.

We are using it in our 13B miata with a 4.88 R&P with 17" wheels. the miata 6spd 4th is slightly shorter and will posiibly drop on, but still not what one is looking for..

https://shop.quaife.co.uk/mazda-rx7-...quaife-gearkit

If anyone's interested.

I found another new option?

P.A.R. close ratio dog gear set for stock FD box.

Very good selection of 4 options of ratios for each gear 1st-3rd.

They say no extra cost for helical cut gears or custom ratios if you want them.

Shown as only $5,456.

RX7DS-SET ? RX7 1st~4th Dog Engagement Gearset ? PAR ? Precision Automation Robotics

Hmmn, that and the Formula Ikeya Sequen shifter is a budget close ratio sequential that could probably take ~500ft/lbs (straight cut).

I did a torque @ wheels graph for it on this thread-
https://www.rx7club.com/single-turbo...1115446/page2/

What I think would be fun to try is to put an RX-8 front case on an FT86/FR-S/BRZ/whatever 6-speed and see if the older Nismo S15 6th gear set will fit. The 2-6 ratio split would end up pretty close to the most common PBS 5-speed ratios (need a different rear end to be truly apples to apples but oh well) and some classes give a weight break for synchro boxes.

Really, it all boils down to adapters. There's not many good close ratio options if you're sticking with synchros, and dogboxes are expensive for anything but takeout NASCAR 4-speeds.

That Quaife gearset is very interesting, thanks for sharing as I did not previously realize they made anything for our boxes. However, do we know if they improved the synchro design to last? Isn't that usually what fails on third gear in our trannies or is it actual gear failure?