Paul Loatman

Does anyone know if this works at high rpms? I can shift without the clutch at low revs but i wouldn't do it at high speeds, just doesn't sound very good for the trans, even with less teeth on the syncros. If it was that simple to get the same effect as a dogbox, i don't see why they would be so expensive.

dj55b

iTrader: (2)

Because they're not. Dogboxes are built to take a serious pounding, and probably use stronger materials to no chatter teeth as easily. And not to mention that dogboxes also weight less.

Rogue_Wulff

Besides the fact that filing off syncro teeth doesn't address the issue of changing the ratios, it also speeds up the rate at which the trans wears out.

As for the question of how difficult it would be, aside from the required milling, which I strongly reccomend having done by an experienced machishist, the rest of the job is about the same as rebuilding a trans. There's a few tools needed that are not in the average persons toolbox, but it is easier to do than rebuilding a rotary engine.
Once the input shaft has been machined to the required specs, the entire Miata trans internals is a direct swap for the RX7 internals.
I have heard that Miata trans internals are not quite as strong as the RX7, but I cannot confirm. It seems the spec miata guys don't have much trans failures, if they take proper care of the car. I'd think the same would apply here.
I would really like to do this myself, combined with either a 4.10 or 4.30 R&P, but I'm just not sure if it would keep me CSP legal. I know the R&P is allowed, but I'm unsure of the trans internals. I could likely sneak by with it, on a local basis. Of course, if I add the camden, I'd be in SM2 anyways.......
The guy who does most of the course setup for our local region drives a Miata, and he does a good job in seting up the course to allow for bumping the rev-limiter in his Miata. This makes me either exceed 8K, or use 3rd gear a couple times per run. Neither are great options.

Whizbang

whats with the competition transmission mazda has listed in their comp. prep. manual?

ratios in that thing were
1st: 2.350
2nd: 1.608
3rd: 1.240
4th: 1.00
5th: 0.881 or 0.839
rev: 2.26

Rogue_Wulff

IIRC, those ratios were actually designed to work best with a rear gear in the 4.88 range.
I believe the complete unit is NLA, but they still sell the internals. Just be prepared to drop ~$5K for the complete set. I'm not sure if the ratios are still the same, though.
A buddy of mine has a 1st gen track car that came with the comp gearset in the trans, and a 4.88 rear gear. Worked well at the road course, but sucked for autox. He has a 3.90 LSD in it for now. Much better for autox, but not as good for the track. 4.88's are going back in, once I have rebuilt it for him, pinion bearing spacer broke, causing a heck of driveline vibration.......

j9fd3s

iTrader: (3)

just looking at the comp box last week, its geared to use different than stock tires as well.

racing beat ran 16x12 wheels, so its more like a 27-28" tire, stock is more like 23"

so anyways 4th gear on the stock trans is about the same as 5th in the comp trans with 4.88's and big tires.

j9fd3s

iTrader: (3)

if you look at the mazdatrix faq, its not very difficult, but you kinda need a lathe.

and dont bring it to a machine shop, cause they get that look, like cutting the stock one is impossible, but they could make a new one out of jam....