I think the issue with the 5spd box is the lack of ribbing. If you ever look at the two its very obvious that the casing of the 6spd is designed for more power. I think the problem is more of a flex in the case straining the internal gearing than the actual gearing being weak.

If both box's were equal in strength I would pick the 5sp box any day. Its one of the best boxes ever built as far as shift feel and natural no think shifting. The 6spd as BB pointed out has very close gear notches and makes you think to shift. I've never missed 3-4 more in any box at the track. IF it had a 1-2 and R lock out for the track it would be ****.

 

Hey Sav; What size tire are you running on your car? Pretty much made my mind up about going with 6 speed.

Think You mentioned the 2001+ six-speeds had a better feeling shift, but is there any real difference between the boxes? Are they equally as strong? For some reason I recall reading the mazdaspeed boxes are cryo-treated gearsets or something of that nature?

 

He's running 225/45/15 NT01's on x9's if I'm not mistaken..

 

Umm, pardon the stupidity, but, is it possible to mate 1.6L to a 6-speed?

 

Yes. Only 2 bolts will match on the starter, but that's OK. You'll need to splice a couple wires together for the reverse and other switches.

 

225/45 NT-01s on 15x9 6ULs.

The MSM boxes are cryotreated and have the best shift feel of any 6-speed, 90% as good as a 5-speed. The red Kraftwerks car I drove at BW last year had an MSM 6-speed and if it weren't for the shift points and gearing, I would never have known it. The 2001 boxes are almost as good. The 99 box I have is noticeably worse than the 2002 box I drove in a friend's car, although I replaced the 5/R shift fork when I had it rebuilt last year and the only shift I used to miss (4-5) is butter smooth now. It's a different gearbox and you have to get used to it, but they are way way stronger. I put a bunch of days at 200whp and a few days at 270whp on my 6-speed and it looked perfect when we had it open.

 

My mystery 6-speed shifts 10x better than my sister's MSM box...significantly better. I have the funky 4-5 shift problem on occasion though.

I frequently drive 5-speed daily and the 6-speed track toy and I'm indifferent to shifter feel.

I've put 8 track events on a 6-speed with no problems. TDR's red 290whp car seems to blow up transmissions once per track event, I'd say no more than 3 days on a 5-speed at the absolute most. He finally gave up on the 5-speed after the micro-polished and cryo treated 5-speed died in the first session at Hallett.

6-speed is the way, there is no fighting it.

 

6- speed fo sho no ifs ands or butts about it. Unless your friend likes having no teeth.

 

Look, ma, no teef!

 

When my 6sp box was out of commission with a messed up 5/R shift fork last year, I had to borrow a tranny for RTA and didn't even consider one of the multiple spare 5-speeds in the backyard. Found a 6-speed to borrow from a friend and helped him install it later on for the favor.

 

Even Matt Andrews ran a 6-speed once or twice at 400+whp and didn't break the thing.

 

At 400whp, I would start looking at an RX tranny swap. Mike's MSM 6 speed started giving him problems at that power level on the street. After 470whp, it's completely trashed.

 

I'd rather spend my money on something like a Jericho at that point.

 

If you need a hook up on 'em, lemme know.

 

Tim -

Maybe you could hook us up by making the adapter parts needed to run the RX7 Turbo II tranny! Still plentiful and cheap at this point. Who else here thinks they'd be used more if there was a regular source for the parts needed to install them?

 

I have naughty dreams of a nebulous car with a high-rpm SBC and a Jericho box.

 

+1

 

I already Faro'ed the spare trans I have. I made a dirty .dxf direct from the faro data a while back. See post 25. I'm sure I posted it here too (I mention a post here at mt.net)
http://forum.miata.net/vb/showthread.php?t=312954

http://www.inoneear.com/outtheother/MazdaBPTrans.DXF

If someone has a RX7 transmission I can measure that too. Clutch, flywheel, etc the more parts I can measure the more accurate and easier it will be to make solid models of everything. I'm sure i can even machine some of the plates here.

 

I have one of the discontinued 8.200 deck height (302 height) aluminum ford SVO race blocks sitting in my office, and a go-ahead by the owner to use it in the miata. It's an old Jesel PRI display so it's already machined for our lifters, rockers, and belt drive. I'm sure there's some CFE heads lying around i could borrow indefinitely too. 9000rpm wouldn't be a problem.

I just got done designing a belt drive for the new RHS aluminum raised cam LS block. About 10 minutes ago Dan (Jesel) said "you know we could put this one in that miata of yours instead" That's going to be sick.

I got the coolest job in the world.

 

That would be sick. 9000rpm aluminum 302 Jesel valvetrian motor with a Jericho dog box = sexy time.