Has anyone looked into Gear changes in 6-speeds?
 

I'm curious about this. A small discussion was started on M-S.com and I'm carrying it over here for all you tech-minded people. I'll try to recap and bring everyone up on what we've found so far.

Mazda 6-speed transmission, Made by Asin, code AZ6
Other models using a variation of this trans:
Honda S2000 (AP1 confirmed, AP2 unsure) , Mazda Miata/MX-5/Roadster, Mazda RX-8 (MkI for sure, MkII not sure), Toyota Altezza/Lexus IS200
Various Ratio's availiable:
Mazda MX-5 gear ratios: 3.760 2.269 1.645 1.257 1.000 .843

Honda Gear ratios: 1st: 3.133 2nd: 2.045 3rd: 1.481 4th: 1.161 5th: 0.943 6th: 0.763

Mazda RX8 Gear ratios: 3.76:1 2.27:1 1.65:1 1.19:1 1:1 0.84:1 (2002)

(2009+) 3.82 2.26 1.54 1.18 1.00 0.79

Lexus IS200/Altezza: 3.874 2.175 1.484 1.223 1.000 0.869

I do know the S2000 AP1 transmission is entirely different externally. You can't swap the center section, the tail shaft is different, as is the bellhousing. I assume internals are very similar. RX-8 Mk1 has identical internals to the AZ6 as confirmed from an outside source.

Also, aftermarket gear set for the 6-speed? Check:
http://www.par-engineering.com/secti...da&sectionId=7

Just bust out the benjamins...

So, I'm not sure if any of it will swap, but who's any idea on the matter? I'm starting to look for some junked other brand transmissions to test it out, and also looking for first hand experience.

Tyia,
~Nick

Wow shit this is great but are there any other aftermarket gearsets that are cheaper than $5000?

Also please give us link t the original discussion

I will be rebuilding my 6 speed in a few weeks so spiff gears might be noice

Pretty cool but if you're building a serious track only car it's more like $7500US as the dog engagement box would be what you want.

Be interesting to find out if you could use the AP1 gearset... looks like more usable ratios for FI Miatas, particularly 1st and 2nd.

6-speed with a 3.63 why would you want to change anything?

Because I fucked my second and third gear synchros to death with 70k miles of unempathic shifting. If I can find something better while the thing is apart, why not go for it?

Just more choices. If for some reason you wanted a crazy cruise gear, or you enjoy the salt flats.

with the 3.63s and tracking, that would put 5th gear topping out at about 135, so you're on a fast track in a fast car using 6th. Might make it fun to have a 170mph gear. Not that it will happen.

But honestly, its just another option hustler. One actual advantage you might find, even with 3.63s and the miata 6-speed is that the AP1/AP2 transmission has nicer engagement, due to Carbon Fiber syncros vs our brass syncros. This is the same trick used in the newest rendition of RX-8 transmission which I believe is an in house mazda design, not related to the AZ6 now with further research.

What carbon fiber syncros offer you is less surface friction from the oil allowing them to perform quicker, making for better gear shifts.

Still a lot of speculation, but I really want / need more info on the AP2 trans as that has all the shiny awesome bits I want. Mainly the .763 6th gear.

The 6speed + 3.6gears are quite nice, especially with an 8k redline. Speaking of which 8k redline with that combo will indeed get you north of 170mph.


Still waiting for that link to the mazdaspeed forums.

Theres not much there that you've not got already, since I did most all the research myself. Oh, I guess I have to embarrass we over there. Linky

http://www.mazda-speed.com/forum2/in...c,22665.0.html

Still thinking that Rx-8 and AP2 transmissions would be lovely to get ahold of.

OH! one more thing to add. Mazda 7" ring gear options. no joke:
Vehicle Year/Model Final Drive
'94-'02 Kia Sportage 4x4 (front axle) 4.778:1
'99+ NZ market Kia Sportage 4x4 (front axle) 4.625:1
'94-'97 Miata 4.10
'99+ Miata five-speed (4.10:1 on automatic starting in 2000) 4.30
'87-'88 Mazda 4x4 truck (front axle) and Kia NZ Sportage optional 4.44
Mazda RX-8 4.44
'79-'85 12a RX-7 and ('99+ six-speed Miata) 3.909
'79-'82 RWD 626 five-speed ('01+ Australian six-speed) 3.636:1
Kia Sportage aftermarket gears are available 4.875:1, 5.125:1, 5.38:1

Probably more useful for silly NA guys wanting stoopid tall gears.

6-speed is perfect as-is. The only thing I could wish for is a taller 3rd to make it a little more usable at 300wtq. 6-speed/3.63 feels doggy to me if the car doesn't make at least 300whp. There's a good reason every fast Cali FI car runs 6-speed/3.909 combo.

If I am going to spend a bunch of money, it's not going to be in a Mazda box - I'm going to step straight into a Jerico 5-speed or something sequential. Every time I look at used Jerico boxes, and then add the bellhousing, TOB, master cylinder, clutch fork, resplined discs, and then compare it to the number of 6-speeds I can buy, I resolve to just keep a spare transmisison or two on hand at all times.

The 6sp/4.10 combo on my car felt like dog shit at 240whp.
Though its a street car so obviously completely different application, but it was just stupid short. The only part of it that I enjoyed was knowing that it wasn't just going to crap out after a couple spirited shifts.
I don't know how much better 3.9 is but going from 4.30 to 4.10 I really didn't notice a significant difference at all. Just my .02

3.6 sounds tempting as hell though.

Find one with a jacked countershaft or something, then steal parts from it. If it is just the 6th gear, you could feasibly swap that out of a nb 6 speed in a couple hours.

It's pretty noticable. Jumping from my GF's MSM (6spd/4.1) to my car (6spd/3.9) is noticable right away..especially 1st and 2nd. In her car I start off in 2nd gear al lthe time....that doesn't work too well in my car. In theory, you could just find any 99/99 special edition or a 01-03 6spd car for sale at a dealership in your area and take it for a test drive. I know it won't be as fast, but you'll get an idea of the gear ratio difference.

I think the 6spds are hit-or-miss on their construction...that or slave cylinders. I have to shift mine kinda slowly, no power shifting whereas the 6spd in my GF's MSM is ultra smooth and slick. I've been wondering if I have a shitty slave and am getting clutch drag or if it's the synchros. I do plan on removing the slave, wollowing out the mounting holes to get it as close to the fork (compressed piston) as possible to see if that stops the potential clutch drag.

I'm hitting just over 65mph in 2nd gear on my 6spd/3.636 and 7800rpm...how can you not love that? 4th is like 116mph or so.

Check this out: http://solomiata.com/Drivetrain.html


Hey my GF has a mazdaspeed too! That 3.9 just sucks horribly, especially paired with the wuss bucket 6200RPM redline. Shifting out of first at 20mph :( :loser:

Clutch drag. What is that? Sounds like something I should explore before taking the thing apart.

^^6500rpm redline / 4.11 rear in an msm. it is an annoying combo.

See, that sounds a bit too tall. I was going to go with a 3.6 set, but now I may go with 3.9. I wanted 3.6 six for the cruising speed in 6th, but I find myself never going on long trips. The sure thing is that I am tired of my 4.1 gears.

Hey tardbucket...the MSM has a 4.1....not a 3.9. You read like you operate a sawzall :giggle:

Clutch drag is when the clutch doesn't fully disengage and has a small amount of pressure still on the flywheel. This can be caused by not enoguh range of motion in the fork or slave cylinder...or a bad clutch (mine is new).

You need to take into account the 7800rpm rev limit. That 65 is more like 59 with a stock rev limit of 6900/7000. Going at the local speed limit of 75, I'm at 3200rpm. There are times where I would like a taller 6th or a 7th gear...mostly because you can go 90 or 100 for several hundreds of miles without being pulled over.

1st
3.760

36.1
2nd
2.269

59.9
3rd
1.645

82.6
4th
1.257

108.1
5th
1.000

135.9
6th
.843

161.2

That is what FM says with a 3.63 and a 6 speed. This is what I am shooting for. It is basically a 5 spd 4.10 with an extra gear.

This is thanks to the FMM gear calculator. Play with it, and see if there are numbers you like.

http://www.flyinmiata.com/tech/gearing.php

The turbocharged S15 Silvia also used an Aisin AZ6 box:
1st: 3.626
2nd: 2.200
3rd: 1.541
4th: 1.213
5th: 1.000
6th: 0.767

It's possible (probable?) that none of the guts of these AZ6 boxes will interchange. If they do... well, I recall a few hi-po Miata 6spds shredding gear teeth. So...

The S15 has more torque, stock, than any other car that came with an AZ6. Which means the stock S15 gears were designed to withstand higher gear tooth loading than the rest. In short, S15 gears are likely stronger than Miata AZ6 gears.

In 1st thru 4th gear, S15 gears + 4.10 rear end has rather similar overall gearing as stock 6spd Miata + 3.9. 5th gets a bit shorter. 6th gets a bit taller.

Might could possibly maybe be an avenue for affordable stronger gears. Or not. Some kind soul would have to determine whether S15 gears have any hope of swapping into a Miata AZ6 box.