RX8 5-speed Transmission strength
07-10-23, 03:09 PM
#1
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RX8 5-speed Transmission strength
My 13B-REW is ready to go into my SA. General consensus is that the RX8 transmission will put the shifter in the perfect spot. There are many threads on here and elsewhere, comparing the 5-speed manual from the overseas 4-port Renesis. Some claim the gearbox itself is identical to the FD box and it just has a different bellhousing and tailshaft. Many also say that is false and that it is just as weak as the 6-speed. Most of these threads are well over 10 years ago. Now that it is 2023, does anyone have a conclusive answer to this argument?
07-10-23, 04:22 PM
#2
The RX-8 4 port 5 speed is definitely a Type R gearbox variant (RX-3, S4 FC, S5 FC, FD).
They handle 350-450ftlbs torque depending on how crazy they are abused.
They strip 3rd gear when torque/traction limit is exceeded.
They do not like constant 8,000rpm plus when racing and take a bunch of HP to turn.
The main issue with FD and RX-8 5 speed variant is lack of transmission mount which causes people to mis shift and damage synchros.
There are two variants of RX-8 6 speed. S1 2004-2008 and S2 2009-2011.
The S2 6 speed is a top loading case, which should be stronger. The main failure I have seen on S1 6 speed is results of broken shift forks from forcr shifting it too hard/fast.
I would choose S2 6 speed myself.
They handle 350-450ftlbs torque depending on how crazy they are abused.
They strip 3rd gear when torque/traction limit is exceeded.
They do not like constant 8,000rpm plus when racing and take a bunch of HP to turn.
The main issue with FD and RX-8 5 speed variant is lack of transmission mount which causes people to mis shift and damage synchros.
There are two variants of RX-8 6 speed. S1 2004-2008 and S2 2009-2011.
The S2 6 speed is a top loading case, which should be stronger. The main failure I have seen on S1 6 speed is results of broken shift forks from forcr shifting it too hard/fast.
I would choose S2 6 speed myself.
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07-10-23, 05:03 PM
#3
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The RX-8 4 port 5 speed is definitely a Type R gearbox variant (RX-3, S4 FC, S5 FC, FD).
They handle 350-450ftlbs torque depending on how crazy they are abused.
They strip 3rd gear when torque/traction limit is exceeded.
They do not like constant 8,000rpm plus when racing and take a bunch of HP to turn.
The main issue with FD and RX-8 5 speed variant is lack of transmission mount which causes people to mis shift and damage synchros.
There are two variants of RX-8 6 speed. S1 2004-2008 and S2 2009-2011.
The S2 6 speed is a top loading case, which should be stronger. The main failure I have seen on S1 6 speed is results of broken shift forks from force shifting it too hard/fast.
I would choose S2 6 speed myself.
They handle 350-450ftlbs torque depending on how crazy they are abused.
They strip 3rd gear when torque/traction limit is exceeded.
They do not like constant 8,000rpm plus when racing and take a bunch of HP to turn.
The main issue with FD and RX-8 5 speed variant is lack of transmission mount which causes people to mis shift and damage synchros.
There are two variants of RX-8 6 speed. S1 2004-2008 and S2 2009-2011.
The S2 6 speed is a top loading case, which should be stronger. The main failure I have seen on S1 6 speed is results of broken shift forks from force shifting it too hard/fast.
I would choose S2 6 speed myself.
07-10-23, 06:32 PM
#4
Id just buy a brand new 2009-2011 RX-8 6 speed.
Thats what I did for my 1993-1995 usdm FD 5 speed. It was about the price of a rebuild for a new transmission.
If you have a certain budget, get whichever you can afford and then dont drive like you are trying to break it.
But a s2 RX-8 transmission isnt a rarity, just not as dirt common as S1.
Thats what I did for my 1993-1995 usdm FD 5 speed. It was about the price of a rebuild for a new transmission.
If you have a certain budget, get whichever you can afford and then dont drive like you are trying to break it.
But a s2 RX-8 transmission isnt a rarity, just not as dirt common as S1.
07-10-23, 07:53 PM
#6
I didnt swap.
I was indicating I went with the option of a brand new transmission purchased through Mazda Motorsports.
I bought a brand new 1993-1995 usdm (tall 5th gear) RX-7 FD transmission. $2,300
Just checked and brand new 2009-2011 RX-8 6 speed transmission is $1,800.
I was indicating I went with the option of a brand new transmission purchased through Mazda Motorsports.
I bought a brand new 1993-1995 usdm (tall 5th gear) RX-7 FD transmission. $2,300
Just checked and brand new 2009-2011 RX-8 6 speed transmission is $1,800.
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07-13-23, 09:47 AM
#7
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The RX8 09-11 6spd is on backorder and may not arrive until next year according to many of the dealers I have called. I'm thinking about doing the RX8 5spd. It seems it has a smaller diameter flywheel/clutch. What options would I have to make this combo work? What flywheel, clutch kit, bell housing, push/pull style slave, and starter would I need. I currently have the FD transmission.
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07-13-23, 07:44 PM
#8
Old [Sch|F]ool
If it truly does have a smaller diameter flywheel and clutch, it sounds like basically a '74-78 5 speed, with the "N/A" sized flywheel and the 22mm spline input.
Mazda made basically four clutches for everything, the 200, 215, 225, and 240mm units. A little flaky on the 200, but they used it in Miatas and earlier cars. There are also basically only two clutch splines, what I will call N/A and Turbo, although of course the 23 spline "Turbo" size was also used on RX-8 6 speed, V6s, etc and the 22 spline "N/A" was used behind four cylinders.
So if I am right, all you need is a nonturbo rotary flywheel and clutch. I think they were only ever made push-type. OR... if you have an FD trans you could use your existing bellhousing and swap the trans to it and just have a 240mm 22 spline disk made.
The only gotcha may be, I have never heard of Mazda using one size input without using its corresponding output, so... you might be able to use your existing driveshaft.
Mazda made basically four clutches for everything, the 200, 215, 225, and 240mm units. A little flaky on the 200, but they used it in Miatas and earlier cars. There are also basically only two clutch splines, what I will call N/A and Turbo, although of course the 23 spline "Turbo" size was also used on RX-8 6 speed, V6s, etc and the 22 spline "N/A" was used behind four cylinders.
So if I am right, all you need is a nonturbo rotary flywheel and clutch. I think they were only ever made push-type. OR... if you have an FD trans you could use your existing bellhousing and swap the trans to it and just have a 240mm 22 spline disk made.
The only gotcha may be, I have never heard of Mazda using one size input without using its corresponding output, so... you might be able to use your existing driveshaft.
Last edited by peejay; 07-13-23 at 07:53 PM.
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07-13-23, 08:59 PM
#9
It should be noted that the RX8 5-spd has narrower gears to compensate for the added synchro rings. Likely not an issue if NA though other than the wide gear spacing, but likely more durable than the 6-spd. It will certainly shift better than the earlier transmissions with the extra synchros.
Both the 6-spd and 5-spd length difference for the RX-8 is substantial though, like 3” or more longer
on the RX8 5-spd you would need to swap out the rear casing and shift rods/tower with the equivalent RX7 parts for it to have the FD3 shifter and PPF positions.
Mazdaspeed also sells the RX8 5-spd bellhousing separately. This makes for an easy conversion to a push clutch on the FD3, not sure about the FC as I’m not very familar with that setup.
.
Both the 6-spd and 5-spd length difference for the RX-8 is substantial though, like 3” or more longer
on the RX8 5-spd you would need to swap out the rear casing and shift rods/tower with the equivalent RX7 parts for it to have the FD3 shifter and PPF positions.
Mazdaspeed also sells the RX8 5-spd bellhousing separately. This makes for an easy conversion to a push clutch on the FD3, not sure about the FC as I’m not very familar with that setup.
.
Last edited by TeamRX8; 07-13-23 at 09:10 PM.
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07-14-23, 09:09 AM
#10
I'll chime in here since I am running a JDM 4 port Renesis with the 5 speed in one of my FB's. I do not have a picture of the clutch and flywheel that came off of that engine since they were pretty worn and I tossed them - but in their place I am running a lightweight flywheel which fits both a Turbo 2 (I had it on one previously) as well as the Rx8. The clutch I am using is also for a turbo 2, the input spline count on the Rx8 5 speed is the same as the T2. Also, the output spline count is also the same as a T2 since I am using a driveshaft which was previously used on a T2 swap.
TeamRx8 - glad you brought up/confirmed info about the thinner gears to make room for the tri-syncro. That's one of the biggest draws to this transmission for me - much smoother shifts than the T2 trans. Just Fyi - the FC is already a push type clutch, so swapping the Rx8 bell housing would only be needed to convert and FD as you suggest.
Chris - assuming you have the REW placed in basically the same location as a stock engine in that SA, the Rx8 5 speed should put the shifter in basically the right spot. It is 3" too far forward to line up in an FB, and I believe SA shifters are about 3" forward - should line up for you. As for the rest of the combo - I would just use the Rx8 trans as is - use the rx8 starter and either a Rx8 or T2 flywheel/clutch, fab a trans mount and such. It should bolt up to the REW with no issues otherwise.
Hopefully this info helps - the Rx8 5 speed is a good transmission for the money, at least so far
The 4 port Rene in front of it is less than thrilling, but it took my car from "not running" to "running" so I'll go with it lol
TeamRx8 - glad you brought up/confirmed info about the thinner gears to make room for the tri-syncro. That's one of the biggest draws to this transmission for me - much smoother shifts than the T2 trans. Just Fyi - the FC is already a push type clutch, so swapping the Rx8 bell housing would only be needed to convert and FD as you suggest.
Chris - assuming you have the REW placed in basically the same location as a stock engine in that SA, the Rx8 5 speed should put the shifter in basically the right spot. It is 3" too far forward to line up in an FB, and I believe SA shifters are about 3" forward - should line up for you. As for the rest of the combo - I would just use the Rx8 trans as is - use the rx8 starter and either a Rx8 or T2 flywheel/clutch, fab a trans mount and such. It should bolt up to the REW with no issues otherwise.
Hopefully this info helps - the Rx8 5 speed is a good transmission for the money, at least so far
The 4 port Rene in front of it is less than thrilling, but it took my car from "not running" to "running" so I'll go with it lolLast edited by 82transam; 07-14-23 at 09:14 AM.
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07-14-23, 09:27 AM
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If it truly does have a smaller diameter flywheel and clutch, it sounds like basically a '74-78 5 speed, with the "N/A" sized flywheel and the 22mm spline input.
Mazda made basically four clutches for everything, the 200, 215, 225, and 240mm units. A little flaky on the 200, but they used it in Miatas and earlier cars. There are also basically only two clutch splines, what I will call N/A and Turbo, although of course the 23 spline "Turbo" size was also used on RX-8 6 speed, V6s, etc and the 22 spline "N/A" was used behind four cylinders.
So if I am right, all you need is a nonturbo rotary flywheel and clutch. I think they were only ever made push-type. OR... if you have an FD trans you could use your existing bellhousing and swap the trans to it and just have a 240mm 22 spline disk made.
The only gotcha may be, I have never heard of Mazda using one size input without using its corresponding output, so... you might be able to use your existing driveshaft.
Mazda made basically four clutches for everything, the 200, 215, 225, and 240mm units. A little flaky on the 200, but they used it in Miatas and earlier cars. There are also basically only two clutch splines, what I will call N/A and Turbo, although of course the 23 spline "Turbo" size was also used on RX-8 6 speed, V6s, etc and the 22 spline "N/A" was used behind four cylinders.
So if I am right, all you need is a nonturbo rotary flywheel and clutch. I think they were only ever made push-type. OR... if you have an FD trans you could use your existing bellhousing and swap the trans to it and just have a 240mm 22 spline disk made.
The only gotcha may be, I have never heard of Mazda using one size input without using its corresponding output, so... you might be able to use your existing driveshaft.
its push type like the FC.
if one wasn't using the Rx8 engine, all of it would go in the bin, and be replaced with T2 stuff
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diabolical1 (07-19-23)
07-14-23, 09:44 AM
#12
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I'll chime in here since I am running a JDM 4 port Renesis with the 5 speed in one of my FB's. I do not have a picture of the clutch and flywheel that came off of that engine since they were pretty worn and I tossed them - but in their place I am running a lightweight flywheel which fits both a Turbo 2 (I had it on one previously) as well as the Rx8. The clutch I am using is also for a turbo 2, the input spline count on the Rx8 5 speed is the same as the T2. Also, the output spline count is also the same as a T2 since I am using a driveshaft which was previously used on a T2 swap.
TeamRx8 - glad you brought up/confirmed info about the thinner gears to make room for the tri-syncro. That's one of the biggest draws to this transmission for me - much smoother shifts than the T2 trans. Just Fyi - the FC is already a push type clutch, so swapping the Rx8 bell housing would only be needed to convert and FD as you suggest.
Chris - assuming you have the REW placed in basically the same location as a stock engine in that SA, the Rx8 5 speed should put the shifter in basically the right spot. It is 3" too far forward to line up in an FB, and I believe SA shifters are about 3" forward - should line up for you. As for the rest of the combo - I would just use the Rx8 trans as is - use the rx8 starter and either a Rx8 or T2 flywheel/clutch, fab a trans mount and such. It should bolt up to the REW with no issues otherwise.
Hopefully this info helps - the Rx8 5 speed is a good transmission for the money, at least so far The 4 port Rene in front of it is less than thrilling, but it took my car from "not running" to "running" so I'll go with it lol
TeamRx8 - glad you brought up/confirmed info about the thinner gears to make room for the tri-syncro. That's one of the biggest draws to this transmission for me - much smoother shifts than the T2 trans. Just Fyi - the FC is already a push type clutch, so swapping the Rx8 bell housing would only be needed to convert and FD as you suggest.
Chris - assuming you have the REW placed in basically the same location as a stock engine in that SA, the Rx8 5 speed should put the shifter in basically the right spot. It is 3" too far forward to line up in an FB, and I believe SA shifters are about 3" forward - should line up for you. As for the rest of the combo - I would just use the Rx8 trans as is - use the rx8 starter and either a Rx8 or T2 flywheel/clutch, fab a trans mount and such. It should bolt up to the REW with no issues otherwise.
Hopefully this info helps - the Rx8 5 speed is a good transmission for the money, at least so far
The 4 port Rene in front of it is less than thrilling, but it took my car from "not running" to "running" so I'll go with it lol
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Chris79SA (07-14-23)
07-14-23, 10:20 AM
#15
Another thing I forgot to mention - the Rx8 uses wheel speed sensors to drive the speedometer. As such there is no provision for the speedo cable on the Rx8 transmission. I am using a Speedhut GPS to cable speedometer drive box. The ford style cable they offer can be easily modified to fit a FB/FC gauge cluster. Just a heads up in case you want to keep the stock cluster in your SA
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diabolical1 (07-19-23)
09-19-23, 12:57 PM
#16
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What is the RX8 5 speed transmission breaking point? I'm in Thailand and have an SR20det swapped RX8, with the SR20 transmission. I'm currently rebuilding another SR20 for 500whp and looking at transmission options.
09-20-23, 09:10 AM
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the Rangers used a bunch of different things, they did use an R box sometimes too (Mazda has a transmission factory and Ford doesn't)
09-20-23, 09:15 AM
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Mazda did a bunch of revisions, so the early ones die a lot, and the later ones its really rare. as per usual out of the 10 or so failures, 5 of them are one guy, who will apparently break every transmission he drives on any car. 3 are another guy complaining about a noise, and maybe its not the transmission?
the point being it really really depends on how you drive the car.
09-21-23, 07:18 AM
#20
as always, it will just depend how abusive it’s treated. I know of 550 whp REW applications using the RX8 5-spd gently that are fine, the same as the FD version. Yet even the RX8 REW swap I now own, sheared the teeth off 3rd gear on same with a BW S362 SX-E hyped up on 25+ psi boost with E50 pushing hard (~550 whp, 300+ ft-lbs) by the previous owner.
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