Miata gears in a FB
08-18-10, 08:52 PM
#1
Miata gears in a FB
Well after having it laying around the house for about a month I finally got it installed.
The bell housing and center section is all S4 rx7, the tail shaft is out of a GSL-SE, the 1st, 2nd, 3rd and 4th gear is out of a 2001 miata transmission, 5th gear is out of the S4. The reason I went with the S4 fifth gear is because it was the tallest one of them all. My highway rpm dropped about 500 rpm, should be a bit better on gas.
The main reason I did this is to battle my second and third gear difference, I used to see about 3krpm difference between those two gears and wasn't making it ideal at the track. now its down to 2krpm difference, and I can go a little quicker in second gear.
If anyone is considering this swap, try to shoot for a 99 or higher miata transmission as second gear in those is actually a double synchro, so more life out of it. As with any other miata gearing swap, the input shaft must be turned down as mentioned on mazdatrix website.
All together, the miata transmission, the cost of the machining and swap done by a shop, was 900$ , I also bought new synchros as we were already inthere and just to be safe, I only.replaced first second and third as they're the most used ones. That was another 150$ or so.
Overall it was definetly money well spent I think. I'm pleased with everything and I hope it helps my track times. I'll be back on the track on Sunday.
The bell housing and center section is all S4 rx7, the tail shaft is out of a GSL-SE, the 1st, 2nd, 3rd and 4th gear is out of a 2001 miata transmission, 5th gear is out of the S4. The reason I went with the S4 fifth gear is because it was the tallest one of them all. My highway rpm dropped about 500 rpm, should be a bit better on gas.
The main reason I did this is to battle my second and third gear difference, I used to see about 3krpm difference between those two gears and wasn't making it ideal at the track. now its down to 2krpm difference, and I can go a little quicker in second gear.
If anyone is considering this swap, try to shoot for a 99 or higher miata transmission as second gear in those is actually a double synchro, so more life out of it. As with any other miata gearing swap, the input shaft must be turned down as mentioned on mazdatrix website.
All together, the miata transmission, the cost of the machining and swap done by a shop, was 900$ , I also bought new synchros as we were already inthere and just to be safe, I only.replaced first second and third as they're the most used ones. That was another 150$ or so.
Overall it was definetly money well spent I think. I'm pleased with everything and I hope it helps my track times. I'll be back on the track on Sunday.
08-19-10, 03:39 AM
#3
NP 
I like to do as much research as possible and then run my own testing also.
Besides these all help me remember what all I have done with the car over the years. If I ever sell this car, I think the new owner would be really happy to have all the documentation. The worst thing that I've ever done though is keep tabs of how much I've spent on the car over the years, without any labor since I do most of the work myself, I'm over 20k$. I tried to calculate it once with labor time, at a conservative rate of 50$/hrs and it turned up to close to 45k$ that's not counting thing like brake pads or oil changes neither and other thing like all the towing charges ...that's another few on its self.
I think its been a good first car(s) and a fun ride. From starting out about 7 years ago not even knowing how to change a tire properly, just towing a car home from the junk yard and tossing it in my driveway because I was frustrated with being banned to ride a motorcycle. To all this, its quite something ... if I ever have kids, I think I'm going to try to teach them all this stuff as early as possible though.
Anyways back on topic,
just to clarify, when I wrote swap done by a shop, I meant cost of swapping the guts, and not the whole thing swapped in the car. Just putting it out there for anyone who's considering doing this and trying to calculate proper cost estimate.
I like to do as much research as possible and then run my own testing also.
Besides these all help me remember what all I have done with the car over the years. If I ever sell this car, I think the new owner would be really happy to have all the documentation. The worst thing that I've ever done though is keep tabs of how much I've spent on the car over the years, without any labor since I do most of the work myself, I'm over 20k$. I tried to calculate it once with labor time, at a conservative rate of 50$/hrs and it turned up to close to 45k$ that's not counting thing like brake pads or oil changes neither and other thing like all the towing charges ...that's another few on its self.
I think its been a good first car(s) and a fun ride. From starting out about 7 years ago not even knowing how to change a tire properly, just towing a car home from the junk yard and tossing it in my driveway because I was frustrated with being banned to ride a motorcycle. To all this, its quite something ... if I ever have kids, I think I'm going to try to teach them all this stuff as early as possible though.
Anyways back on topic,
just to clarify, when I wrote swap done by a shop, I meant cost of swapping the guts, and not the whole thing swapped in the car. Just putting it out there for anyone who's considering doing this and trying to calculate proper cost estimate.
08-19-10, 11:13 AM
#4
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i did a stock gsl-se trans, cause the machine shop guy gave me that "its impossible to do what you're asking" look when i showed him the input shafts...
otherwise i would totally have done the miata gears.
at the track 2-3 are WAY too far apart in the FB box..
otherwise i would totally have done the miata gears.
at the track 2-3 are WAY too far apart in the FB box..
08-19-10, 11:32 AM
#5
j9fd3s - If you ever need that done, let me know, I can get the machining done for you and shipped out. I think the machining cost was only 100$. I have thought about doing about 5 complete transmissions or so and just selling them. But not sure if there's enough interest on that.
08-19-10, 05:28 PM
#6
Bad ***. This is exactly what I'm planning on doing eventually. I was going to go with the T2 gearbox and 4.44's which would be indestructible, but it was going to cost more in the long run than the Miata hybrid box. The other benefit of the Miata box is that the gears line up completely where as in the Rx-7 boxes even though they're the same gears they only line up with 50% gear mesh.
08-19-10, 09:46 PM
#7
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Good research. I have a s2000 and sure is a six speed. But I will love that the rx-7 doesn't drop the rpms so hard between second and third. It's not easy to drop a miata tranny? IF it fits
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08-19-10, 11:16 PM
#8
Lives on the Forum
Nice work Sam! And for anybody who hasn't had the pleasure of experiencing his car first hand, its a real monster.
Keep up the great work man. And I hope to see you over here for another autocross soon.
.
Keep up the great work man. And I hope to see you over here for another autocross soon.
.
08-20-10, 09:54 AM
#12
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they can do it....
08-21-10, 11:35 AM
#14
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nice work i have actually done the exact same thing to my 84 as well as swapp to the 410 rear end gears. the ratios are perfect it feels like the thing just keeps pulling
08-21-10, 01:32 PM
#15
I also currently have the 4.1 rear end in there, but will be swapping back to the 3.9. The reason that I'm doing this is because I drive my car on the highway quite a bit and anything that can bring my cruising rpm down the better. It might only be 100 rpm .. but its still something.
I didn't really see much of a performance difference between the two anyways. I think its not until you get to a 4.7 or so that you would really see a difference.
The new 3.9 rear end has had a REM ISF Finish done to it (Isotropic Superfinishing) Here's a couple videos explaining what that is:
http://www.youtube.com/watch?v=tN9LR...eature=related
http://www.youtube.com/watch?v=UgMJSUOAhvU
In a nutshell its to increase the life of the gear, and reduce friction between the 2 gears. So less heat is produced in the differential increasing life of the rear end oil, along with increasing HP to the wheels by a fraction. I was going to do it to the whole transmission gear set, but didn't have time.
The place that I've been getting all this work done is at Houseman Autosport. Jamie Houseman is extremely knowledgeable with all this Miata gears and can probably build all these things blindfolded now. Here's a link to his site:
http://www.housemanautosport.com/
Also about how the thing accelerates, its definitely nice to stay in the power band. First time I tried it out was on a on ramp. By the time I was on the actually highway I was already at about 115mph! I didn't realize how quick I was going and had to really slow down lol.
I didn't really see much of a performance difference between the two anyways. I think its not until you get to a 4.7 or so that you would really see a difference.
The new 3.9 rear end has had a REM ISF Finish done to it (Isotropic Superfinishing) Here's a couple videos explaining what that is:
http://www.youtube.com/watch?v=tN9LR...eature=related
http://www.youtube.com/watch?v=UgMJSUOAhvU
In a nutshell its to increase the life of the gear, and reduce friction between the 2 gears. So less heat is produced in the differential increasing life of the rear end oil, along with increasing HP to the wheels by a fraction
. I was going to do it to the whole transmission gear set, but didn't have time.The place that I've been getting all this work done is at Houseman Autosport. Jamie Houseman is extremely knowledgeable with all this Miata gears and can probably build all these things blindfolded now. Here's a link to his site:
http://www.housemanautosport.com/
Also about how the thing accelerates, its definitely nice to stay in the power band. First time I tried it out was on a on ramp. By the time I was on the actually highway I was already at about 115mph! I didn't realize how quick I was going and had to really slow down lol.
08-23-10, 09:16 PM
#16
My 7 is my girlfriend.
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Very nice. I'm home til the weekend, gimme a call so I can take her for a spin. And take it easy on the speed, I'd hate to hear the OPP took the thing away from you after all the hard work.
09-05-10, 01:51 PM
#18
When I was on the track with this transmission 2 weekends ago, I was actually 1.5 second quicker with this transmission than the other one, I wasn't having the problem of which gear I should be in anymore.
It appears that second gear is taller and third is shorter (both by 500 rpm in each way), the only issue is, on the really tight slow corners (say something like 40mph) because second is taller now you might be a bit out of power range, but should be back half way through the turn again anyways so not a huge deal. This could also be engine dependent. I only have a 12a Street Ported, maybe a 13b with a bit more torque in that area would still be ideal.
Here's my power output graph for anyone that is a bit more race spirited interested to see if it would work better with their engine's output or not:
It appears that second gear is taller and third is shorter (both by 500 rpm in each way), the only issue is, on the really tight slow corners (say something like 40mph) because second is taller now you might be a bit out of power range, but should be back half way through the turn again anyways so not a huge deal. This could also be engine dependent. I only have a 12a Street Ported, maybe a 13b with a bit more torque in that area would still be ideal.
Here's my power output graph for anyone that is a bit more race spirited interested to see if it would work better with their engine's output or not:
09-05-10, 03:18 PM
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i'm not sure weather to look at the tq curve or the hp curve, but paul yaw used to have something called gearspr its a spreadsheet that lets you plug in the gear ratios, and figure out the rpm drops between gears.
it kind of looks like if you shift @7500, it puts you about 5500, which means you might actually make the car faster trying to get more power in the 5000-6000 range.
it kind of looks like if you shift @7500, it puts you about 5500, which means you might actually make the car faster trying to get more power in the 5000-6000 range.
09-12-11, 10:52 AM
#20
I was typing an email with this and I thought it would be good information to also add in here:
The best years to look for are 99-2005 years as mentioned they have a double synchro in second gear, but from 1990-2005 they all had the exact same gearset. Here's a few gear ratio info:
Vehicle 1st 2nd 3rd 4th 5th
----------------------------------------------------------------------------------
81-83 RX7 3.674 2.217 1.432 1.00 .825
84-85 RX7 12a 3.622 2.186 1.419 1.00 .758
84-85 13b GSLSE 3.622 2.186 1.419 1.00 .807
1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
Miata 5-Speed 3.13 1.833 1.303 1.00 .814
To give you an example of what that means, I personally went from an 84 12a to the miata, using a rear end ratio of 3.9 and tire size of 225/45R15, my original speed at 4500rpm in second gear (2.186 ratio) would of been around 36 mph, with the miata gear (1.83 ratio) at the same rpm I would be at about 43 mph. Looking at a higher rpm this time, at 7500 rpm with the stock gearing of second I would of been at 60mph, with the miata gear that brings me up to 72mph.
Might be easier to put this into a chart actually:
84 RX7 Miata
-----------------------------------------------------------------
4500 2nd gear 36mph 43mph
7500 2nd gear 60mph 72mph
5500 3rd gear 68mph 74mph
7500 3rd gear 93mph 101mph
Here's also another way to look at it which might be a better way to show things. I'll be matching the same speed (mph) shifting from 2nd to third and showing rpm drops for shifting at about 67mph in both transmission
84 RX7 Gear 8400 RPM in second gear -- shift up to third doing ~ 67 MPH -- 5500 RPM in third gear (2900 RPM Drop)
Miata Gear 7000 RPM in second gear -- shift up to third doing ~67MPH -- 5000 RPM in third gear (Only a 2000 RPM Drop)
I hope that helps you understand the difference the actual gearing difference.
The best years to look for are 99-2005 years as mentioned they have a double synchro in second gear, but from 1990-2005 they all had the exact same gearset. Here's a few gear ratio info:
Vehicle 1st 2nd 3rd 4th 5th
----------------------------------------------------------------------------------
81-83 RX7 3.674 2.217 1.432 1.00 .825
84-85 RX7 12a 3.622 2.186 1.419 1.00 .758
84-85 13b GSLSE 3.622 2.186 1.419 1.00 .807
1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
Miata 5-Speed 3.13 1.833 1.303 1.00 .814
To give you an example of what that means, I personally went from an 84 12a to the miata, using a rear end ratio of 3.9 and tire size of 225/45R15, my original speed at 4500rpm in second gear (2.186 ratio) would of been around 36 mph, with the miata gear (1.83 ratio) at the same rpm I would be at about 43 mph. Looking at a higher rpm this time, at 7500 rpm with the stock gearing of second I would of been at 60mph, with the miata gear that brings me up to 72mph.
Might be easier to put this into a chart actually:
84 RX7 Miata
-----------------------------------------------------------------
4500 2nd gear 36mph 43mph
7500 2nd gear 60mph 72mph
5500 3rd gear 68mph 74mph
7500 3rd gear 93mph 101mph
Here's also another way to look at it which might be a better way to show things. I'll be matching the same speed (mph) shifting from 2nd to third and showing rpm drops for shifting at about 67mph in both transmission
84 RX7 Gear 8400 RPM in second gear -- shift up to third doing ~ 67 MPH -- 5500 RPM in third gear (2900 RPM Drop)
Miata Gear 7000 RPM in second gear -- shift up to third doing ~67MPH -- 5000 RPM in third gear (Only a 2000 RPM Drop)
I hope that helps you understand the difference the actual gearing difference.
09-12-11, 11:36 AM
#21
Waffles - hmmm good
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I was typing an email with this and I thought it would be good information to also add in here:
The best years to look for are 99-2005 years as mentioned they have a double synchro in second gear, but from 1990-2005 they all had the exact same gearset. Here's a few gear ratio info:
Vehicle 1st 2nd 3rd 4th 5th
----------------------------------------------------------------------------------
81-83 RX7 3.674 2.217 1.432 1.00 .825
84-85 RX7 12a 3.622 2.186 1.419 1.00 .758
84-85 13b GSLSE 3.622 2.186 1.419 1.00 .807
1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
Miata 5-Speed 3.13 1.833 1.303 1.00 .814
To give you an example of what that means, I personally went from an 84 12a to the miata, using a rear end ratio of 3.9 and tire size of 225/45R15, my original speed at 4500rpm in second gear (2.186 ratio) would of been around 36 mph, with the miata gear (1.83 ratio) at the same rpm I would be at about 43 mph. Looking at a higher rpm this time, at 7500 rpm with the stock gearing of second I would of been at 60mph, with the miata gear that brings me up to 72mph.
Might be easier to put this into a chart actually:
84 RX7 Miata
-----------------------------------------------------------------
4500 2nd gear 36mph 43mph
7500 2nd gear 60mph 72mph
5500 3rd gear 68mph 74mph
7500 3rd gear 93mph 101mph
Here's also another way to look at it which might be a better way to show things. I'll be matching the same speed (mph) shifting from 2nd to third and showing rpm drops for shifting at about 67mph in both transmission
84 RX7 Gear 8400 RPM in second gear -- shift up to third doing ~ 67 MPH -- 5500 RPM in third gear (2900 RPM Drop)
Miata Gear 7000 RPM in second gear -- shift up to third doing ~67MPH -- 5000 RPM in third gear (Only a 2000 RPM Drop)
I hope that helps you understand the difference the actual gearing difference.
The best years to look for are 99-2005 years as mentioned they have a double synchro in second gear, but from 1990-2005 they all had the exact same gearset. Here's a few gear ratio info:
Vehicle 1st 2nd 3rd 4th 5th
----------------------------------------------------------------------------------
81-83 RX7 3.674 2.217 1.432 1.00 .825
84-85 RX7 12a 3.622 2.186 1.419 1.00 .758
84-85 13b GSLSE 3.622 2.186 1.419 1.00 .807
1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
Miata 5-Speed 3.13 1.833 1.303 1.00 .814
To give you an example of what that means, I personally went from an 84 12a to the miata, using a rear end ratio of 3.9 and tire size of 225/45R15, my original speed at 4500rpm in second gear (2.186 ratio) would of been around 36 mph, with the miata gear (1.83 ratio) at the same rpm I would be at about 43 mph. Looking at a higher rpm this time, at 7500 rpm with the stock gearing of second I would of been at 60mph, with the miata gear that brings me up to 72mph.
Might be easier to put this into a chart actually:
84 RX7 Miata
-----------------------------------------------------------------
4500 2nd gear 36mph 43mph
7500 2nd gear 60mph 72mph
5500 3rd gear 68mph 74mph
7500 3rd gear 93mph 101mph
Here's also another way to look at it which might be a better way to show things. I'll be matching the same speed (mph) shifting from 2nd to third and showing rpm drops for shifting at about 67mph in both transmission
84 RX7 Gear 8400 RPM in second gear -- shift up to third doing ~ 67 MPH -- 5500 RPM in third gear (2900 RPM Drop)
Miata Gear 7000 RPM in second gear -- shift up to third doing ~67MPH -- 5000 RPM in third gear (Only a 2000 RPM Drop)
I hope that helps you understand the difference the actual gearing difference.
FSM to be sure but thats what I remember anyway.
09-12-11, 01:07 PM
#24
If someone really can't find anything nearby, then I'll be willing to help them out, but do look out for an expensive shipping cost ...