Miata Transmission
Joined: May 2002
Posts: 5,972
Likes: 37
From: Ottawa, Soviet Canuckistan
Short-throw shifters are available for the FB tranny, for the shorter shift.
As for the smoother shift, get some RedLine MT-90 manual transmission oil. That smooths it out a bit.
I don't know if anyone tried the miata tranny, but I'd imagine it'd be more trouble than it's worth just for a "softer" feel. Besides the FB trannies are practically industructable under 250hp.
Jon
As for the smoother shift, get some RedLine MT-90 manual transmission oil. That smooths it out a bit.
I don't know if anyone tried the miata tranny, but I'd imagine it'd be more trouble than it's worth just for a "softer" feel. Besides the FB trannies are practically industructable under 250hp.
Jon
Senior Member
Joined: Jun 2002
Posts: 558
Likes: 0
From: Minnesota
Do all FB trannies feel lumpy because thats just the way they are, or is it because they are all 18+ years old? (i.e. if I were to rebuild an FB tranny using all new parts, would it feel smoothe?)
Old [Sch|F]ool
Joined: May 2001
Posts: 12,862
Likes: 568
From: Cleveland, Ohio, USA
A Miata transmission is a bolt in.
All you'd need is the Miata transmission and a donor FB transmission. You'd need to change the front and rear trans housings.
You won't gain the Miata shifter, in other words. But you will gain better synchros and MUCH closer gearing. You might not like that part... 3.91 rear gears and RX-7 trans has the same first gear overall ratio as 4.78 rear gears and Miata trans.
All you'd need is the Miata transmission and a donor FB transmission. You'd need to change the front and rear trans housings.
You won't gain the Miata shifter, in other words. But you will gain better synchros and MUCH closer gearing. You might not like that part... 3.91 rear gears and RX-7 trans has the same first gear overall ratio as 4.78 rear gears and Miata trans.
Trending Topics
spoon!
Joined: Sep 2002
Posts: 1,208
Likes: 50
From: Dousman, WI
Uh, no. Miatas use 4.30 rear gears, except for 94-97 that has 4.10.
What he means is that you have to step up that high to have a same total ratio; the 1st gear on the '7 is 3.622 (or 3.672 on the SAs) while the Miata is 3.176. 2nd-4th are the same between the Miata and FB.
Makes me wonder if that would actually make 1st gear useful in a roadrace / autocross kind of setup. Probably not really. The synchros would be nice though.
I have to ponder bodging together stuff from a RWD 626, a Miata, and an FB now. Can't be *TOO* impossible to swap gears around...
What he means is that you have to step up that high to have a same total ratio; the 1st gear on the '7 is 3.622 (or 3.672 on the SAs) while the Miata is 3.176. 2nd-4th are the same between the Miata and FB.
Makes me wonder if that would actually make 1st gear useful in a roadrace / autocross kind of setup. Probably not really. The synchros would be nice though.
I have to ponder bodging together stuff from a RWD 626, a Miata, and an FB now. Can't be *TOO* impossible to swap gears around...
The trans in my Rx7 has a 81 RWD 626 internals. Very nice semi-close ratio gearset. Even closer than Miata. All gears are usable. The 3rd ->4th is a very nice close ratio. I love rowing thru those gears. Do a search in the race section for RWD 626 on how it is done.
Although 626 RWD boxes are hard to find, when you do find one, it's usually in very good shape. They were economy cars afterall. Mine only needed a few shifter forks + seals.
Last I checked a USED 6 speed Miata trans was 2000 - 3500
Although 626 RWD boxes are hard to find, when you do find one, it's usually in very good shape. They were economy cars afterall. Mine only needed a few shifter forks + seals.
Last I checked a USED 6 speed Miata trans was 2000 - 3500
yes. and RWD 626's were built 79-82.
How to install the guts of a 79-82 RWD 626 tranny into a
81-85 Rx-7 case
From the 626:
Forks
Anything not mentioned below
From the Rx-7:
Shift Rods
Shift lever & ****
81-85 transmission case and bellhousing
626 or Rx-7 Bearings
Might need the 626 center bearing plate, some people say they need it, other's don't.
Mazdacomp and others say the splines 626 input shaft is too long, and needs to be machined down to the same length as the Rx-7 shaft. Approximately 1/2", but measure to be sure. You are machining the splines back only, you are not shortening the input shaft.
Because the 79-82 RWD 626 and 79-80 Rx-7 both use the long shift lever that's positioned further forward in the car, if you have a 79-80 Rx-7, all you need to do is slap a 79-80 Rx-7 bellhousing onto the 626 transmission, shorten the input shaft, and you're ready to go.
I had a problem with my third gear. It jammed stuck in 3rd gear and did not want to come out. On further inspection we found that there must have been something in the 626 case that allowed the 3rd gear shift rod not to slide back all the way. The rx7 case had no such thing (it was fixed mechanically elsewhere in the tranny). So we lathed a groove on the 3rd gear shift fork and put an e-clip on there so the e-clip would bump into the center section of the case, thus preventing shift rod from sliding back too far and jamming.
And we found out that the shift forks from a 1st gen rx7 were exactly the same as the 626. We replaced two 626 forks with rx7 ones.
Gear ratio's on the 626 tranny:
3.214 1.818 1.296 1.000 0.860
I got this off Mazspeed.com awhile ago:
626 box to 1st gen only conversion.
You need from your rx7 box:
* bellhousing / case.
* clutch pivot.
* tail housing.
* selector rods.
* gear stick.
Modifications:
You need to taper the front of the input shaft approx 7mm back further than it already is. Measure from the front face of the 7 box to the back edge of the taper before you pull it apart then transcribe this measurement when the 626 guts are put into the housing.I marked mine with masking tape and ground it back using a 4" angle grinder. A bit ruff but it did the job.
The rx7 tail housing and selector shafts are needed to get the gearstick in the right place.
I think I had a problem with one of the selector falks hitting on the tail housing which with a little attention from the affore mentioned grinder, fixed the problem but be careful in regards to the reverse light activation parts on the selector. My reverse lights come on for 5th gear as well as reverse so I disconnected the light. It would be best if you could get this working properly while the box is out of the car maybe using a multimeter to see when the switch is being activated.
I have run this box for about 8 sprint meetings now as well as my daily driver with a 200 hp 13b with no trouble.I previously asked the question of relyability on this site and got favourable responces.
In aus rx7 boxes are $450, 626 boxes are $220.
Good luck.
tony.
How to install the guts of a 79-82 RWD 626 tranny into a
81-85 Rx-7 case
From the 626:
Forks
Anything not mentioned below
From the Rx-7:
Shift Rods
Shift lever & ****
81-85 transmission case and bellhousing
626 or Rx-7 Bearings
Might need the 626 center bearing plate, some people say they need it, other's don't.
Mazdacomp and others say the splines 626 input shaft is too long, and needs to be machined down to the same length as the Rx-7 shaft. Approximately 1/2", but measure to be sure. You are machining the splines back only, you are not shortening the input shaft.
Because the 79-82 RWD 626 and 79-80 Rx-7 both use the long shift lever that's positioned further forward in the car, if you have a 79-80 Rx-7, all you need to do is slap a 79-80 Rx-7 bellhousing onto the 626 transmission, shorten the input shaft, and you're ready to go.
I had a problem with my third gear. It jammed stuck in 3rd gear and did not want to come out. On further inspection we found that there must have been something in the 626 case that allowed the 3rd gear shift rod not to slide back all the way. The rx7 case had no such thing (it was fixed mechanically elsewhere in the tranny). So we lathed a groove on the 3rd gear shift fork and put an e-clip on there so the e-clip would bump into the center section of the case, thus preventing shift rod from sliding back too far and jamming.
And we found out that the shift forks from a 1st gen rx7 were exactly the same as the 626. We replaced two 626 forks with rx7 ones.
Gear ratio's on the 626 tranny:
3.214 1.818 1.296 1.000 0.860
I got this off Mazspeed.com awhile ago:
626 box to 1st gen only conversion.
You need from your rx7 box:
* bellhousing / case.
* clutch pivot.
* tail housing.
* selector rods.
* gear stick.
Modifications:
You need to taper the front of the input shaft approx 7mm back further than it already is. Measure from the front face of the 7 box to the back edge of the taper before you pull it apart then transcribe this measurement when the 626 guts are put into the housing.I marked mine with masking tape and ground it back using a 4" angle grinder. A bit ruff but it did the job.
The rx7 tail housing and selector shafts are needed to get the gearstick in the right place.
I think I had a problem with one of the selector falks hitting on the tail housing which with a little attention from the affore mentioned grinder, fixed the problem but be careful in regards to the reverse light activation parts on the selector. My reverse lights come on for 5th gear as well as reverse so I disconnected the light. It would be best if you could get this working properly while the box is out of the car maybe using a multimeter to see when the switch is being activated.
I have run this box for about 8 sprint meetings now as well as my daily driver with a 200 hp 13b with no trouble.I previously asked the question of relyability on this site and got favourable responces.
In aus rx7 boxes are $450, 626 boxes are $220.
Good luck.
tony.
Joined: Dec 1999
Posts: 7,855
Likes: 517
From: Behind a workbench, repairing FC Electronics.
Banned. I got OWNED!!!
Joined: Aug 2002
Posts: 4,666
Likes: 2
From: chatsworth,Ca.
i installed a miata tranny into one of my cars....its not bolt in.... you have to switch the tail shaft and bellhousing witch is mayjor work and you have to grind the input shaft down 1" to fit the rotary motor!!! not worth the closer 3rd gear ratio!!!!
p.s. the speedo was off too!! waste of my time if you ask me!!
p.s. the speedo was off too!! waste of my time if you ask me!!
Yeah, shutup kid.
Joined: Mar 2002
Posts: 1,686
Likes: 2
From: Columbus, OH
Originally posted by 680RWHP12A
i installed a miata tranny into one of my cars....its not bolt in.... you have to switch the tail shaft and bellhousing witch is mayjor work and you have to grind the input shaft down 1" to fit the rotary motor!!! not worth the closer 3rd gear ratio!!!!
p.s. the speedo was off too!! waste of my time if you ask me!!
i installed a miata tranny into one of my cars....its not bolt in.... you have to switch the tail shaft and bellhousing witch is mayjor work and you have to grind the input shaft down 1" to fit the rotary motor!!! not worth the closer 3rd gear ratio!!!!
p.s. the speedo was off too!! waste of my time if you ask me!!
Originally posted by 680RWHP12A
i installed a miata tranny into one of my cars....its not bolt in.... you have to switch the tail shaft and bellhousing witch is mayjor work and you have to grind the input shaft down 1" to fit the rotary motor!!! not worth the closer 3rd gear ratio!!!!
p.s. the speedo was off too!! waste of my time if you ask me!!
i installed a miata tranny into one of my cars....its not bolt in.... you have to switch the tail shaft and bellhousing witch is mayjor work and you have to grind the input shaft down 1" to fit the rotary motor!!! not worth the closer 3rd gear ratio!!!!
p.s. the speedo was off too!! waste of my time if you ask me!!
The shop I went to for my 626 box charged me like $290 for the labor and rebuild parts and didn't charge me for the rx7 trans parts or case he used because he has so many laying around. 626 box was $125. FANTASTIC ratios; worth every penny.
