Another 6 speed bites the dust. - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-18-2013, 05:53 AM   #81
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Has anyone looked into Gear changes in 6-speeds?

It's been done - apparently. Would love to see a write up on this.

Edit - Ap1/2 has been done... Not sure about the AZ6, but I'm sure I have read somewhere of this being done.
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Old 10-18-2013, 06:35 AM   #82
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I'd be willing to donate via PayPal to see if this works BBundy.
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Old 10-18-2013, 10:10 AM   #83
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I want to see rx8 transmission swap
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Old 10-18-2013, 10:32 AM   #84
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Quote:
Originally Posted by bbundy View Post
The center section looks like the same exact casting wonder if the Miata belhousing, tailstock, and shifter linkage would bolt up like early NA rx7 boxes do with the Miata 5 speed?
I know where a couple very dead RX8 transmissions are. I bet I could get the guy to give me one. I wonder if I could turn up a dead Miata 6sp to borrow the tail shaft and bell housings from...

I would just send you the RX8 bits and let you worry about it, but I'm 2500 miles away from you and it would cost seven fortunes.

Last edited by vehicular; 10-18-2013 at 10:43 AM.
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Old 10-18-2013, 11:24 AM   #85
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Quote:
Originally Posted by glade View Post
I'd be willing to donate via PayPal to see if this works BBundy.
Actually I could use that sort of encouragement My car budget credit card is maxed out right now and I cant afford anything till the first of the month.

Good news is RX8 6 speeds seem to run a few hundred less than Miata 6 speeds.

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Old 10-18-2013, 11:45 AM   #86
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But the RX8 2nd gear synchro is ****. I need to replace mine, I know a guy that went through 3 and another on his second. Just be warned. You can find 6-speeds used on rx8club.com for 300 - 600 but that synchro is a iffy. I intend to swap mine out with an 09+ trans next year.
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Old 10-18-2013, 11:48 AM   #87
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How much power are these transmissions holding on those cars? Does anyone think they're as strong as a TII?


I can use a Miata 6spd in my project with about the same modification time as the TII will require, but the TII being stronger and way cheaper, i threw that out pretty quick.

If the RX8 trans halves that difference and is TII strong, but better-feeling 6spd vs. vaguely truck-y 5spd, i'm down with that. Would work well with a 3.23-ish. Plus then, if we're using Miata tails, that cut downs on fab work for install, as well as being able to use off the shelf V8R driveshaft.


If you want to get real crazy, the BRZ/FRS twins use a derivation of the AZ6 trans as well.

Last edited by concealer404; 10-18-2013 at 12:05 PM.
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Old 10-18-2013, 12:03 PM   #88
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They use the same guts as the RX8 transmission with a slightly different case. ISC Racing has rebuilt a bunch of them and claims it isn't a very reliable transmission in racing for the RX8s. But he can definitely rebuild them.
Bob, your car is fast but you fail at reading. ^This is from much earlier in this same thread.

I sure am glad you guys figured out what I already told you. The RX8 six speed and Miata six speed are almost identical except for the cases. This from a shop that builds Spec Miatas, RX8s, and RX7s for SCCA.
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Old 10-18-2013, 12:08 PM   #89
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They're unreliable in a 3050lb RX8, but they might have some margin in a 2300lb Miata.
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Old 10-18-2013, 12:22 PM   #90
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Quote:
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They're unreliable in a 3050lb RX8, but they might have some margin in a 2300lb Miata.
Very true. My point was, and is, that they were pretty much the same internally.
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Old 10-18-2013, 12:23 PM   #91
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Quote:
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They're unreliable in a 3050lb RX8, but they might have some margin in a 2300lb Miata.
When you double engine torque, that margin disappears.
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Old 10-18-2013, 01:07 PM   #92
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Quote:
Originally Posted by flying_solo View Post
But the RX8 2nd gear synchro is ****. I need to replace mine, I know a guy that went through 3 and another on his second. Just be warned. You can find 6-speeds used on rx8club.com for 300 - 600 but that synchro is a iffy. I intend to swap mine out with an 09+ trans next year.
From the parts listing on Mazda Comp the RX8 and the miata have the exact same part numbers for the second gear syncro and shift fork. The gear has a different part number but it is the same ratio.
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Old 10-18-2013, 01:26 PM   #93
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Quote:
Originally Posted by sixshooter View Post
Bob, your car is fast but you fail at reading. ^This is from much earlier in this same thread.

I sure am glad you guys figured out what I already told you. The RX8 six speed and Miata six speed are almost identical except for the cases. This from a shop that builds Spec Miatas, RX8s, and RX7s for SCCA.
What portion of the case. The front and back are different sure. The center looks the same. I need some hard evedence like pictures of how their different not just second hand hearsay.

Last edited by bbundy; 10-18-2013 at 01:51 PM.
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Old 10-18-2013, 04:35 PM   #94
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Input spline
Miata 15/16" -22
RX8 1" -23
RX7 TII 1" -23
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Old 10-18-2013, 05:53 PM   #95
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So, no bueno then?
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Old 10-18-2013, 05:55 PM   #96
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Interesting.... that would imply that the RX8 is some weird mix of an AZ6 and an "R box."

Also means it has the right shaft diameter and spline for my project.
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Old 10-18-2013, 06:07 PM   #97
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Quote:
Originally Posted by bbundy View Post
Input spline
Miata 15/16" -22
RX8 1" -23
RX7 TII 1" -23
This maybe good news. Shaft diameter is the same size as RX7. Only need to change only your clutch disk and pilot bearing. Now the big question is the bellhousing, input shaft length, tail housing and output shaft
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Old 10-18-2013, 06:58 PM   #98
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Some more discoveries. S15 Silvia SR20DET
Stock HP/Tq 245/202 at just 7 lbs of boost. Note: same exact center casting as the 6 speed miata. Note web site shows some mix and matched sections of these transmissions bolted together.
AZ6 Family.
S15 6 spd 3.626 2.200 1.541 1.213 1.000 0.767
NISMO 2.907 1.989 1.537 1.218 1.000 0.862
RX8 6 spd 3.760 2.269 1.645 1.187 1.000 0.843
Miata 6-spd 3.760 2.269 1.645 1.257 1.000 0.843
SXE10 6 sp 3.874 2.175 1.484 1.223 1.000 0.869
TRD 3.106 2.175 1.585 1.223 1.000 0.869
See more at: 6speed option for your Toyota "A"powered rwd car: Grassroots Motorsports forum: Classic Motorsports



S15 Silvia SR20DET Transmission, same center section as Miata.
Attached Thumbnails
Another 6 speed bites the dust.-img_8558_zps6a8014e4.jpg  
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Old 10-18-2013, 07:13 PM   #99
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I like the TRD ratios better than the Miata ratios. And the S15 has a taller top gear for someone who didn't have 3.63s already.
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Old 10-18-2013, 08:27 PM   #100
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Quote:
Originally Posted by sixshooter View Post
I like the TRD ratios better than the Miata ratios. And the S15 has a taller top gear for someone who didn't have 3.63s already.
6th gear looks really easy to swap actually same part numbers between the RX8 and the Miata for those gears.

S15 box with the miata 6th swapped in looks pretty good too for gear ratios to me.

I cant figure out what the TRD transmission is out of images of Altezza transmissions I can find look different.
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