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Old 10-17-2013, 12:53 PM   #61
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Lesher Motorsports Inc. Spec Miata rentals and builds

I dunno what kinds of work he normally does. He was instructing at the MRLS event (I was pitted next to him), and happened to have a few transmissions in his shop when people needed them.

--Ian
Funny that is exactly where I got this box that I just broke from. First day broke 4th in session 3 on the front straight. Paid a ridiculous amount to get a Mazdaspeed transmission delivered to the track and I had it in the car in time to run the last session of the day.

Last edited by bbundy; 10-17-2013 at 02:14 PM.
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Old 10-17-2013, 01:33 PM   #62
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Looking at Quaife you also have Elite to consider, slightly cheaper boxes.

One of my paddock buddies is running an Elite IL300 6S EVO 2 ($8k) behind a 380bhp Rover 8 and when it has failed it has been vibrations, bolts etc and the service form Elite have been great.

Elite lists a number of Gear kits, so they might be one of many companies to contact for a quote for a set or single pairs of gears.

Would new tougher gears for 3rd and 4th be enough to make the 6sp tough "enough", or would a full set be better to do it right at once (labor etc cost the same regardless of how many gears you change)?
Making 3rd-6th gapped for track, 2nd for standing starts and 1st for loading would be nice. Aiming at 4.1:1 diff to have easily accessible rear end options
Personally I'd be pleased with a 6sp mated to my 4.875. I never see speeds where the 6th would run out on our tracks (at my power level...).

I never got anyone to bite on the flawed option of changing final drive to reduce the torque in the box and move some of the driving breaking 4th into 5th. Would it just make the thing break anyway or would it change the time spent on sensitive gears (breaking less boxes per time bu spending more time in 5th).
I hit just over 7100 rpm in 6th with the 6 speed 3.636 combo at Pacific Raceway. You must run on tiny go-cart tracks by comparison.
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Old 10-17-2013, 02:17 PM   #63
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I hit just over 7100 rpm in 6th with the 6 speed 3.636 combo at Pacific Raceway. You must run on tiny go-cart tracks by comparison.
Yup, longest straight .7mi on our longest 2.5 mi track.
Roughly 7000rpm when braking (ancient 5speed now).
All other tracks have top speeds around 110mph (and most are around 1.3 mi long).

Not enough power and "anti aero" helps to keep the speed low.

Then there are no quick fixes...
Designing a Bulletproof Manual Transmission - Gear Solutions Magazine
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Old 10-17-2013, 03:00 PM   #64
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Odd. I had been talking to PAR on and off for a few years. Their old website had info for AZ6 (6 speed) straight cut dog and helical syncro conversion, bilet shift forks, etc. Now it's just 5 speed stuff. I'm sure they can still do the AZ6 stuff if you ask. Wasn't cheap though. By the time you did a full gearset with billet forks and got it here, it would be around $6K.

I shipped a pallet full of dead AZ6's to Ron Olsen at BAR in IL about 6 months ago. He's working on a sequential box. Problem is his goal is an EP box so barely able to deal with 180lbs tq. When I told him there was a slightly larger market for turbo Miata guys he was interested.. until I told him it had to survive 400 lbs and 300° for about 30 minutes.

I've heard of guys modifying T5's to hold more torque and adapting them. Those are dirt cheap. Available ratios suck though.

Coolest option is a Quaife QBE60G 6 speed sequential. They even offer a bell housing and input shaft for our B series Mazda engine. Bare bones set up would probably run $9K. Cool guy set up with shifter and electronic controls for anti-overrev, flat shift, etc, would push that to about $13k.

Oh yeah, I have a customer in Australiar that put an RB26 Skyline trans into the Miata. I believe the SR20DETT engines S15 Skyrine used a variant of the AZ6. RB26 was something different.

So yeah, I don't have any answer either.

PAR is good people. Of course, i'm biased, because they seem to be the only people that have come up with a solution to make the old shitty Mazda G-series trans hold together. Yeah, it's a lot of money, yeah, we could swap to a Toyota E153 for cheaper, but sometimes, that's just not legal in the rules set.

I'm considering buying their 3rd gear for my daily driver.




Myself, for my NA, i'll be using an FC TII transmission. I doubt it'll see heavy track time like many of you guys, but it's going to be subject to some pretty brutal forces in the torque area of things.
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Old 10-17-2013, 03:05 PM   #65
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Is there a problem with the regular Quaife gearsets for the 5 speed? Savington ran one at ~350whp on track for a while right? It aint cheap, but nothing in this thread is.
I own a Quaife WR 5-speed, but haven't used it yet. Bought it on an impulse with the hope that it would be stronger, but there's little more than anecdotal proof either way on that IMO. I never actually used anything beyond an OE 6-speed, and I was on my second one when I paused development on Theseus ~2yrs ago.

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Old 10-17-2013, 03:12 PM   #66
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But the "ratios suck" according to Emilio and Sav (TKO ratios similar to T5z). Sav explained why in a different thread discussing the T5...I disagree but I drive my car on the street.
From M.net a couple of years ago:

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Both, but for different reasons. The best you will ever do with a T5z box (2.95:1 1st gear) and a 3.636 rear end is a 1st gear combined ratio of 10.72:1.

I know from experience that:
1. At 220whp, with a 6sp/4.10s, 2nd gear will hook on pavement in warm weather. That's a 9.30:1 ratio
2. At 270whp, with a 6sp/3.909s, 2nd gear will usually hook on pavement in warm weather - not always, but usually. That's a 8.87:1 ratio
3. At 350whp and 300wtq, with a 6sp/3.909s, 2nd gear will spin from any speed in any weather

If the best possible 1st gear ratio in a T5 box is a 10.72:1, and I can spin a 8.87:1 with 270whp, 1st gear will still be unusable - so why bother doing the swap?

The tall 5th gear may be nice - you end up at around 2500rpm in 5th, vs 3150rpm in 6th (with 3.636:1 gears in both cases). The question is whether you would end up lugging the motor at 2500rpm, since you're so far off the torque peak at that point. I wouldn't be even slightly surprised if there were a fuel mileage loss by running the motor so slowly. Remember that LSx motors get away with this because they make such huge torque down low - engines are most efficient near their torque peak.

Road Race 5-speed

For track cars, the issue lies in the 2nd gear ratio. On a road course with a 5-speed, 2nd gear is limited to very slow-speed corners, and about 50% of the time it can be just as fast to leave the car in 3rd instead. With 200+whp and a 5-speed, you will almost never use 2nd gear, since you always have enough torque to make 3rd work. The ratio in the 5-speed is 1.888:1 - the T5 box makes this WORSE, since 2nd gear is a 1.94:1 in the T5z box and a 1.89:1 (IIRC) in the Camaro box. The 3-4 gears are just about the same (1.34 vs 1.33 and 1.0 vs 1.0), but if the usable ratios are the same in the T5 as the stock 5-speed, and you aren't breaking the 5-speed, why in the world would you bother doing the swap?

Road Race 6-speed

With a 6-speed, we use 3rd as the low-speed gear, since it's tall enough to be usable in the situations where you would be between 2nd and 3rd with the 5-speed. The ratio is 1.645:1, and even in the higher power cars (300whp+) it's usable - you have to be a little gentle with the throttle, but it's still a usable gear. This gives you 4 great ratios: 3rd (1.645), 4th (1.257), 5th (1.0), and 6th (.843), and as a result a Miata with a 6-speed is faster around a road course than a Miata with a 5-speed.

With the T5 box, you lose a ratio, because the 1.89/1.94 2nd gear ratio is simply not usable on a road course with anything more than 200whp. You're forced to use 3rd gear instead, and you're limited to 3 usable ratios - and even that assumes you are wealthy/smart enough to opt for the 0.82:1 "road race" overdrive, instead of the .6x:1 highway overdrive that comes standard (looks like a 0.68, 0.64 or 0.63 depending on which box you use). If I am going to spend a bunch of money on a bellhousing, T5Z/TKO-600 gearbox, new clutch discs, a driveshaft, a diff mount solution, and a shifter, I'm not going to settle for sub-par gear ratios, and IMO the T5 ratios are significantly inferior to the factory 6-speed ratios. I've explored the option of having a custom 2nd gear made for a Tremec TKO-600 box (something like a 1.55:1 gear, instead of the factory 1.89;1), which would give the same ratio spread as the 6-speed, but for now that's not a cost-effective option - you're looking at $2300 for a new TKO600, plus the cost of having a bespoke gear made, plus bellhousing, clutch discs, driveshaft, and all of the other items that are required for the swap.

For now, the 6-speeds are reliable enough to race on, and cheap enough to carry a spare in the trailer. Once the power levels in Theseus rise to the point where the 6-speeds become a regular consumable, we'll look at spending the coin to get a proper swap put together, but until then, we'll continue to recommend the 6-speed for all applications - it has a more usable "1st" gear than a T5 for the street guys, and more desirable ratios for the road race guys.
If I'm spending $4-5k on a bombproof gearbox, I'm not going to tolerate subpar ratios.
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Old 10-17-2013, 04:09 PM   #67
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Are you sure it wasnt an RB25 transmission? RB26 only came with 4wd transmissions. The gearbox from the r33/r34 skyline and turbo VG from the z32 300zx gear boxes can take quite a bit of abuse and are the go to for RWD nissans putting out high power. Normally wanted for power above 250kw and are known to last quite well even when copping abuse from cars putting out over 300kw. Torque figures would be a whole lot more useful but they aren't thrown around much. Dont know the kw to hp conversion off the top of my head, but you can work it out. Anyway the demand inflates their price so they probably aren't the most suitable option, esspecially not in America.

The 6 speed nissan gearbox from the s15 silvia has a reputation for being quite weak. Far weaker than the earlier 5 speed. People can't agree if its torque or abuse that kills the 6 speed.
Sorry for taking it off topic, just being ----.
Not from an email so I can't fact check it. It was a phone conversation with a racer from Australia. Definitely said it was a Skyline box. Thought he said it was from the 6 cylinder and not the SR20, not sure on that. I only mentioned it in case someone else knew more details about such a swap. He's over 400whp with that box so apparently it's working.
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Old 10-17-2013, 06:25 PM   #68
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Anybody look at RX8 transmissions? Looks like the 04-08 has the same gear ratios as the miata 6 speed accept curiously 4th gear.


Transmission
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Old 10-17-2013, 07:40 PM   #69
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Originally Posted by Savington View Post
If I'm spending $4-5k on a bombproof gearbox, I'm not going to tolerate subpar ratios.
Just to add a little fuel to the T5 fire, what about upgrading to a stronger rear diff with numerically lower gearing? Something around a 3.23 like shown on the FM calculator?

Flyin' Miata : Technical info : Gearing calculator
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Old 10-17-2013, 08:16 PM   #70
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Anybody look at RX8 transmissions? Looks like the 04-08 has the same gear ratios as the miata 6 speed accept curiously 4th gear.


Transmission
Looking closely at pictures the center sections look Identical between the RX and the Miata 6 speed. looking up detail parts numbers on Mazda comp though most everything has different part numbers for gears and such however so I am skeptical if this is true.

Wouldn’t it be magical if you could buy an RX8 transmission which cost less than a Miata 6 speed as far as I could tell? Bolt on the front and rear sections from the Miata 6 speed. And end up the same with the same transmission as the Miata 6 speed with a slightly different 4th gear that was magically stronger than the Miata one.

I'm tempted to buy an rx8 transmission to check things out.
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Old 10-17-2013, 08:39 PM   #71
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Originally Posted by bbundy View Post
Anybody look at RX8 transmissions? Looks like the 04-08 has the same gear ratios as the miata 6 speed accept curiously 4th gear.


Transmission


Rotation woes? Thought the 06+ spun ccw...
edit; nvrmnd, was thinking mx5.
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Old 10-17-2013, 08:40 PM   #72
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Wouldn’t it be magical if you could buy an RX8 transmission which cost less than a Miata 6 speed as far as I could tell? Bolt on the front and rear sections from the Miata 6 speed. And end up the same with the same transmission as the Miata 6 speed with a slightly different 4th gear that was magically stronger than the Miata one.

I'm tempted to buy an rx8 transmission to check things out.

That would be awesome. It certainly feeds into the dream when you see that every ratio is identical except the one that breaks.
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Old 10-17-2013, 08:47 PM   #73
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Looking closely at pictures the center sections look Identical between the RX and the Miata 6 speed. looking up detail parts numbers on Mazda comp though most everything has different part numbers for gears and such however so I am skeptical if this is true.

Wouldn’t it be magical if you could buy an RX8 transmission which cost less than a Miata 6 speed as far as I could tell? Bolt on the front and rear sections from the Miata 6 speed. And end up the same with the same transmission as the Miata 6 speed with a slightly different 4th gear that was magically stronger than the Miata one.

I'm tempted to buy an rx8 transmission to check things out.
Sound like you got the spare tail and bellhousing from one of the dead solders so why not give it a whirl.
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Old 10-17-2013, 09:20 PM   #74
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I hit just over 7100 rpm in 6th with the 6 speed 3.636 combo at Pacific Raceway. You must run on tiny go-cart tracks by comparison.
your *****
are big

i never went that fast even with 3.9 ratio. thats over 150mph.
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Old 10-17-2013, 09:39 PM   #75
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your *****
are big

i never went that fast even with 3.9 ratio. thats over 150mph.
My ***** were real big when I decided 4th was too low of gear for turn 2 and I started doing it in 5th. But this got me into GT2-GT3 lap record territory. ~13 seconds under spec Miata lap record and doing it with the boost turned down to keep it under 330 rwhp. My car is also heavy for an NA track car ~2525 with driver.
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Old 10-17-2013, 09:41 PM   #76
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Rotation woes? Thought the 06+ spun ccw...
edit; nvrmnd, was thinking mx5.
Does the mx5 spin the other way? didn't know that.
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Old 10-17-2013, 11:06 PM   #77
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Bbundy, what are your problems with the TII swap? That transmission will easily hold your power levels without question. The final gear shouldn't be much different than that of a 6 speed, realistically. I'd like to talk to you about it more, I think it could easily solve your problems. Those transmissions are inexpensive and most of the cost comes in our plate. Let me know if I can help you further or PM me if you have more questions. Best of luck in your search
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Old 10-18-2013, 12:01 AM   #78
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Originally Posted by Savington View Post
I own a Quaife WR 5-speed, but haven't used it yet. Bought it on an impulse with the hope that it would be stronger, but there's little more than anecdotal proof either way on that IMO. I never actually used anything beyond an OE 6-speed, and I was on my second one when I paused development on Theseus ~2yrs ago.
Quote:
Originally Posted by Savington View Post
If I'm spending $4-5k on a bombproof gearbox, I'm not going to tolerate subpar ratios.
Yeah, I know I'm relating an anecdote, but at least it's first-hand: My Quaife gear set has been completely bulletproof. I've autocrossed, drag raced (blowing up my Torsen in the process) and driven on a track in anger. The ratios are wonderful, giving me approx. 75 mph in 2nd gear and a top speed of almost 160 mph (I'm gearing limited, not drag limited, btw). The only complaint I have is that the semi straight-cut gears are noisy, but that's not an issue for a track car. On the highway, I just put in ear plugs.

Six years and still going strong.
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Old 10-18-2013, 01:17 AM   #79
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Interesting reading my RX8 book.

“The Type Y6M Six speed manual transmission is a reinforced high torque version of the 6 speed transmission first employed in the MX5 Miata developed jointly by Aisin-AI and Mazda, and manufactured and supplied by Aisin.”

Specification differences seem to be triple cone synchronizers on the first 3 gears instead of the first two and the 4th gear is 1.187 instead of 1.257. All other ratios are the same. Interesting the weak gear in the Miata 6 speed is the only gear that is different in what is supposed to be a higher torque rated box.

The RX8 isn’t particularly high torque but it came with a 4.444 rear ends and 4” bigger diameter wheels than the Miata so the torque in the drive shaft is much higher than a Miata and the engine rpm is also higher 8500 rpm rev limit stock.

The center section looks like the same exact casting wonder if the Miata belhousing, tailstock, and shifter linkage would bolt up like early NA rx7 boxes do with the Miata 5 speed?

Last edited by bbundy; 10-18-2013 at 02:12 AM.
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Old 10-18-2013, 01:36 AM   #80
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The center section looks like the same exact casting wonder if the Miata belhousing, tailstock, and shifter linkage would bolt up?
Just do it!
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