michael_santiago@hotmail.com

I have an 85 12a, my 2nd gear went out, I'm going to pull the transmission to rebuild it, is any parts upgrades that I can use to make it better?

trochoid

iTrader: (6)

Unless you plan on racing, stock parts are about alll there is.

j9fd3s

iTrader: (3)

since mazda still uses bascially the same transmission still in the mx5, they have had many small upgrades over the years.

the important one being the center countershaft bearing changing from a dual row ball bearing to a roller, its much longer lived.

the shop manual is pretty good, but it does lack pictures, i would recommend taking a bunch when you are pulling the thing apart, as the spacers and snap rings go in order and its not always clear in the pics.

you also should replace the snap rings that hold the input shaft bearing, and the main shaft nut as its staked down.

as far as tools go, a puller with really long fingers is great, although if you're creative its not needed. mazda also has a special lOOOOOOOOOOOONg socket for the main shaft nut, although i have used a wrench. good set of snap ring pliers, feeler guages, big hammer and you're good to go....

mjm4jc

Google "KD Rotary" here in New Tripoli, PA. They specialize in RX-7's and has done a few rebuilds for David Lane's 300 hp turbo GSL-SE. I know David was happy with the results. If you call them, they can answer any tranny rebuild questions you have.

Mike

yellow_jacket

Of you could just drive around the countryside near Allentown and you'll find a huge lot with FD's in it.

That's how I found it by accident. Unfortunately they were closed, but I had nothing for them to do for me anyway.

David Dewhurst

iTrader: (2)

If you were to make a slight change to the Miata 5 speed transmission main shaft length you would have much better ratios than the 1st gen transmission has. With the change to the shaft length the guts from a Miata 5 speed will fit right into the 1st gen transmission.


If you would like the required new shaft length plerase e-mail ddewhurst1 at wi.rr.com

jinxed4dub

iTrader: (7)

Ok I've been wondering this for awhile, I'm sure the answer is no, but can a rx8 or a mx5 six speed bolt up. I'd like a six speed.

j9fd3s

iTrader: (3)

the rx8 and 2000-2005 miatas 6 speed boxes are similar, but basically they share nothing.

so the rx8 trans has the rotary bellhousing, so it will bolt to the engine. it takes a t2 clutch and flywheel. the rx8 starter motor is different, but a t2 might be made to work. driveshaft is t2 size.

the bad bits... the shifter is further forward than the FB, so it would fit better in an SA. the rx8 uses a powerplant frame like the FD, so you need to fab a simple mount, and i bet its in a different place than the FB/SA.

also the rx8 uses the abs sensors for wheel speed, so theres nothing in the trans.

and after all that 6th gear is SHORTER so it revs HIGHER on the freeway

jinxed4dub

iTrader: (7)

So its alot of work for basicly nothing is what your saying. so the sixth gear doesnt have more top speed than 5th? then whats it for? I beleave what your saying, and I remember nfs underground the 6th gears always slowed you down when on the top end drag racing. I'm just curious. I just wanted to change up gear ratios and was thinking to compensate for loss of top speed add a gear, but **** it who needs more than 120 mph. I've had a fast car, and I've had a quick car, and in the long run the quick car was alot funner since you dont get to drive 170 everyday but I get on the freeway onramp often enough. Not to mention the consiquences that may occure at those speeds other than the ticket, jail time, impond, ect...

thunkrd

iTrader: (1)

LOL... nfs underground. that game isn't very realistic

j9fd3s

iTrader: (3)

the americans add another gear on top of 5th, and end up with this huge overdrive, but the rest of the world keeps the same first and top, and adds a gear in the middle, so the box is closer ratio.

or to put it another way the rx7 trans is geared a lot like the competition SA/FB trans except its got a granny gear first

jinxed4dub

iTrader: (7)

I'm not saying its realistic, but when you were shifting manualy if you hit 6th gear it would up the rpm rather than add another gear. I thought it was a stupid game glitch but I guess its not, and the games actually more realistic than I thought. dirt and grid are the two most realistic racing games, but there all just games. I just never driven a 6 speed gearbox except in nfs and videogames.
But I don't even own a nintendo. I go to my friends house let him spend all that money.

rotordave

iTrader: (1)

You're living in the 90s! If you want realism, you need to look at rFactor or GTR.

So there are no bits you can get to do a gearbox rebuild at all?

Siraniko

iTrader: (13)

+1 except I shortened the miata's input shaft. so there is no need for a pilot bearing.

Jeezus

iTrader: (4)

You have to shift too fast in a 6 speed. The Miata's lose about a grand when normally shifting, maybe 1500 at redline. I talked to my mazda guy who races Miata's in the SCCA, and he says that the 5 speed is an all around better gear box than the 6. You stay more in your power range, quicker, and handles more power.

David Dewhurst

iTrader: (2)

***+1 except I shortened the miata's input shaft. so there is no need for a pilot bearing.***

Only a wackyracer would do this^.