codrus

IIRC, the stock T5 is *rated* at 300 ft-lbs. The Mazda 6-speed is rated at considerably less.

--Ian

EO2K

iTrader: (37)

^^ This. Ian gets it.

If you are destroying 6 speeds you probably need to stop being a cheap bastard and pony up for a legitimate transmission solution.

As to if the T5 is that solution remains to be seen.

thumpetto007

iTrader: (15)

If people are spinning 3rd (spinning to me is unuseable traction throughout the gear) at 300whp, they don't have the right setup.

There is a guy running a turbocharged ls motor that hooks just fine, and thats a miata with over 650rwhp. When he's on the shitty 205 street tires, of course he spins past 120.

sorry I can't link any photos, I'm still at work.

But the lack of a good transmission completely dissuaded me from doing a high power build with my miata. I just decided to do suspension, brakes, cooling and convinience mods.

patsmx5

iTrader: (16)

I spun 2nd from a roll and 3rd if I hit it hard before I put drag radials on my car. Now it hooks in 1st with ease and it's around 300whp.

I hope Corky brings this to market and doesn't price it so crazy high that he only sells 3 of them. The miata community needs a good transmission solution.

Corky Bell

A couple dimensions:

Shaft Length from the front face of the bearing retainer: 5.71 inch

Spline Dia. 1.065 inch, 10 splines

Pilot bearing ID to fit T5 shaft: .67 inch, or 17 mm

The sleeve dia for the ID of the TOB slider: 1.433 inch

Configuration of the housing allows the front to back dimension to be varied. If you have a specific need, I can probably make it.

corky

aidandj

iTrader: (5)

Rough price estimate?

AlwaysBroken

The only dimension my wife will care about is the size of the hole it drills through the checking account.

EO2K

iTrader: (37)

Slick, makes sense. Hopfully people can just tell you the source vehicle and you can fab up a bell housing.

So I'm going to make some assumptions here, correct me if I'm wrong...

You reversed the location of the clutch fork pivot from the stock DS location (on a Mustang anyway) to PS (as on the Miata) so I assume you are using the Miata fork/pivot/TOB/hydraulics, correct? I think I see the mounting bosses on the side of the bell housing for the slave mounts.

"A new TOB sleeve" above I assume refers to the tube that goes around the input shaft? This is I assume a custom part that allows the use of the Miata TOB with the off the shelf T5 input shaft. Did I get that right?


(random internet T5 shaft pic)

In the above pic, the sleeve is part of the front bearing retainer. Is that the case with your custom part, or is this a cut-and-weld operation?

SO based on my assumptions above...

Miata flywheel
Miata pivot
Miata fork
Miata TOB
Miata slave
Miata starter

Custom bell housing
Custom input shaft sleeve/front bearing retainer
Custom clutch (Miata disc with T5 input splines)
Custom pilot bearing
Custom driveshaft
Custom PPF solution

OEM T5 input shaft
OEM T5 transmission

Did I get that about right?

TurboTim

iTrader: (9)

I only want to know about the shift extender thru the rear 'freeze' plug. I wasn't able to figure that one out easily (that didn't require complete disassembly of the case to swap in a longer shift rod), at least not in a way that was correct.

My 5th synro is junk after about 5k street miles in my brandy new T5z with it's .63 5th ratio. It's too big of a jump when shifting at typical miata engine shift rpms, even with a relatively light aluminum flywheel & clutch package. Sooooo if anyone does this, install the ~.80 5th ratio.

aidandj

iTrader: (5)

.8 isn't bad. Similar to 6 speed.

Leafy

iTrader: (1)

Yup, and unlike 6 speeds, stock t5s break at under the factory rating even in drag race cars. I wouldnt even waste time with this swap doing it with the stock t5 gears, not even a t5z. Astro or nothing.

Corky Bell

Just about spot on.....

In the above pic, the sleeve is part of the front bearing retainer. Is that the case with your custom part, or is this a cut-and-weld operation?
No cut or weld. A new bushing to stuff into the Miata TOB.

SO based on my assumptions above...

Miata flywheel Yes
Miata pivot Yes
Miata fork Yes
Miata TOB Yes, but with new sleeve
Miata slave Yes
Miata starter Yes

Custom bell housing
Custom input shaft sleeve/front bearing retainer No
Custom clutch (Miata disc with T5 input splines) Yes
Custom pilot bearing Off the shelf, different ID
Custom driveshaft Yes
Custom PPF solution Yes

OEM T5 input shaft Yes
OEM T5 transmission More specific, use those fit to Mustangs

Did I get that about right? Yes Sir.

Add in a rear cross member for the tranny..... part of the ppf attach
And the shift lever relocation: Stock T5 lever & pivot, new extension and anchor.

Sorry, but I can't price it out yet. That kinda stuff confuses me.

corky

2manyhobyz

iTrader: (4)

I think you meant to say "especially" in drag race cars. The guys that I've spoken with have said you have to be north of 500hp and launch like an *** hat before you start think of building the trans. Couple that with the fact of how much lighter the Miata platform is it seems unlikely that we would put more stress on a T5 than their platform would. Rebuild to get the gear ratios you want, well that's different. Sorry dude, I'm calling bullshit on that one.
In post 50,
" The new T5 cost $1,295 when I bought it about two years ago. I'll dig out the specific PN and dealer shortly. This is the same piece that we used in the Turbo Mustangs 15/ 20 years ago. The 600 to700 hp did bust a couple second gears and cases, but no(t) often.
I think it is fair to suggest any torque rating can handle an excess of 50%. We had to use a 1.5 margin on helicopter parts, and an easy argument suggests the margin would likely be higher on an automobile. Real racing transmission makers often use a design margin in excess of 5."
I'm thinking maybe, just maybe, Mr. Bell has put his foot down on more horsepower than you've ever thought about.

Roda

Waaay back in the day, I used to drag race a 5.0 Mustang. 400+hp, 4800rpm launches on drag slicks, lifting the front wheels kind of abuse (at 3000lbs w/driver). The only thing that was regularly a problem was 3rd gear, which you could easily kill with an imperfect powershift. When you killed 3rd, 5th and reverse usually followed almost immediately. That was with the 3.35 1st gear stock trans.

I don't think I would worry about it too much in a roadrace Miata, unless you're running huge power, huge slicks, and shift like an asshat.

AlwaysBroken

The idea of doing a high rpm clutch dump launch on slicks in the miata scares the **** out of me. I'd be worried about getting hit by debris.

aidandj

iTrader: (5)

Its the wheelhop that will get ya. Fix wheelhop. Go fast.

SchmoozerJoe

iTrader: (2)

I'd go through stock T5s in my 250hp/225tq '89 fox body on a regular basis... and that was before the nitrous.

Usually it'd be third gear that decided to grenade on me.

And, I wasn't even "that" hard on the drag strip launches... 2.0 sixty foots on street tires.

Monk

iTrader: (3)

85-89 World Class T5s were considerably weaker.
90 and up WCT5s are what we should be looking at.

Leafy

iTrader: (1)

Road race is a bigger issue. You'll do like 4 seasons worth of drag racing abuse in a single road racing weekend. Dont forget that in the time span that Bundy broke 12 6 speeds road racing with 360hp theres been a 640hp drag racing miata yet to break one.

jmann

Bob's problem is more then just hp issues. I have nearly the sane hp and have had no issues with my six and do numerous track days each year. I have helped Bob replace a few of his trans in years past. I think running 275 hoosiers and mainly hard on and off the power doing mainly autocrossing has more to do with his trans issues then just shear hp or tq..