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1979 Mazdacomp Close Ratio Trans

Old 08-08-18, 12:00 PM
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1979 Mazdacomp Close Ratio Trans

Hello, Writing this for a friend that has a '79 SA race car. Years back the clutch and flywheel grenaded and bent the input shaft of the transmission. Apparently these things are harder to find than hens teeth, unicorn horns, (insert hard to find thing here)...

From talking with him, somewhere around 5 of these 12a close gear ratio mazda comp transmissions were made. Below is what happens when the clutch and flywheel spontaneously disassemble.

Hoping to get some more eyeballs and brains on this to find out if there are any suitable replacements out there, either:

A: Someone has one of these transmissions and is willing to part with it.
B: Could an FB/FC/FD input shaft work with modification or direct swap?
C: Could an NA/NB Miata input shaft work?

I can ask to get dimensions if someone has something they think might work.
Thank you



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Old 08-10-18, 11:01 AM
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Miata NA/NB input shaft will work, you just need the nose machined down to look like the one you have there.

One reason that these were not popular is because you can just put the miata gears in the rx7 case and machine the input shaft like above and have a close ratio trans. Pretty much any RX7 running in SCCA Eproduction has either miata gears or a full dog box like emco, pbs, etc...
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Old 08-12-18, 11:26 AM
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the part you're looking for is 4352-17-201. they made many more than 5 of these transmissions

dimensionally its going to be the same as any other rotary M box input shaft, but the gearing was different, so the gear might be different.

you might look into straightening it, in the piston world they straighten crankshafts, and in the Ferrari world they have to straighten heads and cams too
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Old 08-12-18, 05:45 PM
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How many teeth are on it? I have a feeling that it's going to be pretty different from any street production car.

Coarse-gear 1st-gen (S1/S2) have 17 teeth, fine gear (S3/4/5) have 22 teeth, Miatas have 21 teeth. I might be able to get you an OD because there may be pitch changes as well. (A 17 tooth gear to mate with a 29 tooth gear will have a different diameter than, say, a 17 tooth gear that mated with a 27 tooth gear.)

Smoothcase 626 apparently had 18 teeth. I do know that the 626 gearset was the "go to" race gearset before the Miata parts were available, since they had the closest 2-3-4-5 splits. (Still technically closer than Miata although the difference is minor)

Last edited by peejay; 08-12-18 at 05:47 PM.
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Old 08-13-18, 12:23 PM
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There are a couple of guys that have used this gear set in KC. So not that rare. Call Mazda Motorsports https://store.mazdamotorsports.com/w...0001&langId=-1

If your friend is building a competition car and can show what they are working on, they should be able to get credentials to buy parts
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Old 08-14-18, 11:48 AM
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Everyone, thanks for the information. This is an existing race car, in the owner's words, " the 7 was built for GT3 in '83....1999 in paddock at watkins glen, throttle stuck, million rpm ,clutch gave up, no scattershield , fuel line cut, fuel all over and surprise.... ignited."

I forwarded this info back to him and will update as he is able to get spline counts, measurements or luck with finding that part number through mazda motorsports.

Much appreciated!

Edit: Straightening is complicated by a hairline crack. It might be weldedable, stress relieved and straightened if all other options fail.

Last edited by swbtm; 08-14-18 at 11:50 AM.
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Old 08-14-18, 02:45 PM
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the 4352-17-201 is NLA, the good news is that Mazda made a ton of these transmissions, basically everyone seriously racing in the 80's got one. its rare, but not 1/5, more like 1/1000
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Old 08-19-18, 05:11 PM
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You could also post your question on prodracing.com They plenty of Rx7 racers on there site that maybe able to help you.
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