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Old 02-17-2010, 06:06 AM   #1
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Default Which gearbox for Race / Trackdays?

Hi,

a friend of mine from the German mx-5 board with a 99/00 with GT2560R running at ~11-12 psi constantly eats his 5-speed gearboxes. (Always looses 3rd gear)

Look Ma, no teeth...






We have a quite long thread now at the German borad but there are not too many track-driving turbo-equipped cars over here.

He is running a lot of trackdays at The Ring so he really puts a lot of track-use to the gearboxes...

What would you recommend him to do?

- 6-speed
- 5-speed or 6-speed oil-cooled with external oil-cooler
- FM gearbox
- other options

Thanks for the advice (especially from all the Track-gurus...)
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Old 02-17-2010, 06:11 AM   #2
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6-speed, no question. Every fast Cali track car runs one. My 5-speed lasted 6,000 miles, and my 6-speed has been in its place for 25k+. I rebuilt it a couple months ago due to a botched shift - I moved the seat forward a bit after repainting the car and my normal backhanded 5-6 motion found the reverse gate at ~130mph. I got to inspect the internals while we were going over the damaged parts - everything looked great, even after a year of hard track use. We replaced the reverse gear, slider, synchro, and the 5-R shift fork, and left everything else in place. I do not baby the gearbox, either.

Reliable, cheap, and proven fast. Not often that combo comes along. If you can, source a gearbox from a Mazdaspeed Miata, or at least from a 2001+ car - they have better shift feel than the earlier boxes do.
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Old 02-17-2010, 06:19 AM   #3
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What rear end ratio are you using?

Currently, this guy is running a five speed wth a 3.63 rearend, giving him a top speed of 165mph and he flats out...

With the 6speed, he would lose topspeed...are there any options on a plug and play lower gear set? I've heard rumours about the 3.3 diff, some say it fits, some say it won't...

Remember, we're from Germany, so here's is actually the possibility to do that kind of speed...
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Old 02-17-2010, 07:25 AM   #4
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The question is not whether the 3.308 fits - it's whether it exists at all. Some say it does, others have searched and say it does not. 6-speed and 3.63s with a 7400rpm rev limiter gives you 165mph worth of gear to play with.

I am using a 3.909 as is everyone else, with the exception of one 4.10 car. I tried the 3.63s and didn't like them - IMO you need at least 300whp to make them work, and probably closer to 325-350whp. For my goals, I'll stick with the 3.909s.
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Old 02-17-2010, 10:58 AM   #5
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Andrew, who makes the 3.63 gear or is it available from another model? Exactly the gear ratio I am looking for...
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Old 02-17-2010, 10:59 AM   #6
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Quote:
Originally Posted by thagr81 us View Post
Andrew, who makes the 3.63 gear or is it available from another model? Exactly the gear ratio I am looking for...
Old manual 626s had them but finding one is like looking for hen's teeth. Mazdaspeed sells them for $400.
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Old 02-17-2010, 11:13 AM   #7
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Thanks hustler... I will keep an eye out for one. Maybe if I can get ahold of one, I have have Richmond Gears make a duplicate in a more durable material for my setup as they are local. /thread jack
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Old 02-17-2010, 11:23 AM   #8
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Thanks hustler... I will keep an eye out for one. Maybe if I can get ahold of one, I have have Richmond Gears make a duplicate in a more durable material for my setup as they are local. /thread jack
I believe richmond gear looked into this with a group buy in m.net a few years ago and not enough people ponied up the cash to make it worth-while for them to produce any.
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Old 02-17-2010, 12:12 PM   #9
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Yeah, I found that thread on M.net. Might be able to talk them into it as I have buddies who do rock crawling and some of the employees there hang out with them. Worth a shot at least... If I can get it to happen I will post a thread to gauge the interest of maybe having more than 2 of them made.
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Old 02-17-2010, 05:39 PM   #10
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Quote:
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Andrew, who makes the 3.63 gear or is it available from another model? Exactly the gear ratio I am looking for...
This gear comes with all 6speed Miatas in Europe...

There are a lot of people here who are willing to sell or trade it, as a common swap here for autocross + twisties is the 6speed combined with a 4.1 or even a 4.3.

The 4.3 for the big housing isn't available at all here...
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Old 02-17-2010, 06:04 PM   #11
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Hi,
i´m the guy with the 3rd Gear Overdrive Gearbox. :-)

You can find the 3.6 diffs in every 6speed mx5 in germany/europe, like the anni,sportive models. The most people here change from 3.6 to 4.1, so sometimes you can get a complete 3.6 rearend for about 300-400€ at ebay.

With the Combi 5Sp and 3.6 i can use all 5 gears completely. I drive at the nordschleife and the nürburgring gp-course with this setup and i think its quicker for me to shift between 3-4-5, than 3-4-5-6. But you are right, its not quick, if i stay with a broken 3rd gear at paddock.

Tryed someone only to cool the oil of the 5sp down, or installed oil-nozzels for the gears? I measured at my rearend housing 248°F and i think the gearbox is not cooler.
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Old 02-19-2010, 06:51 PM   #12
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I switched to a 6 speed after going through no less than seven 5 speeds. And Ive broken 3rd gear, 2nd gear and the gear that runs the secondary shaft for everything but 4th in different transmissions.

I always ran a short shifter with an extended shift **** in my 5 speed and I really liked it. I rigged it up to work in the 6 speed but found it interesting that the for aft movement feels like the right amount of throw but the side to side movement is way too tight, the distance the **** moves between the 1 and 3 gate is just ¾” . My first attempt at driving an autocross in anger with the 6 speed 3.909 combo required a couple shifts into third because the gearing is too low to stay in second for most autocrosses. Twice I hit 1st while accelerating and trying to hit 3rd. never done that before. With the 5 speed hitting 5th instead of 3rd was the occasional issue but it wasn’t so violent of a mistake as this. I really dont like the stock shifter any more because it feel way too far from the steering wheel and burried low in the tunnel.

With this gearing I doubt I will ever need to use second on a track any more but the 3rd through 6th ratios probably will be better than what I had before with second through 5th on the 5 speed. Just got to make sure I hit the right gears. For autocross the gearing just sucks most everything will require lots of shifts between 2nd and 3rd gears. If I had the money I would get the Quafe.

Bob
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Old 02-19-2010, 08:59 PM   #13
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Quote:
Originally Posted by thagr81 us View Post
Andrew, who makes the 3.63 gear or is it available from another model? Exactly the gear ratio I am looking for...
I have one but havent put it in yet, i ended up getting everything on m.net for about 750. Ill keep you posted, even though I'm defiantly not Andrew. Mazda comp has them, and they were factory in the Aussie 6 speed and 79-82 626.
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Old 02-20-2010, 03:36 AM   #14
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You won't find much info from me on the 3.63s, unfortunately - I am very happy with my 3.909s and I have no plans to switch any time soon. You can get them out of 626s, or if you want a fresh set Mazdacomp has them.
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Old 02-20-2010, 05:12 AM   #15
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I have the quaife trans gears on the track bitch w/a 3.9 torsen. I had a '99 w/6speed and I absolutely HATED the feel of the shifter. First gear was completely useless, even on a street car and was just plain annoying to use. It does seem to be a more robust transmission though, so if $ is tight I would go with the 6spd unless you like to waste your time R&R'ing your transmission every other track event.
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Old 02-21-2010, 09:53 PM   #16
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I ahve a 6 with 3.63. I like the ratios because there is not so much shifting (I'm a bitch), and the rpm drop is much more relaxed on the highway. If my car were a copy of SavingAIDS, I'd possibly put the 4.10 back in, but even that is doubtful.

You'll get accustomed to the shifter with a little time. I have a 5-speed daily and I prefer the feel of the 5-speed outright, but I'm very comfortable with the 6-speed shifter and have no complaints.

I would not buy anything from Quaife. I bought a diff from them for my VW and it broke almost immediately and they would not warranty it. I've also done enough work on a car with a Quaife in it that I would never buy it, even if it were the same price as a 6-speed.
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Old 02-26-2010, 07:12 PM   #17
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with 400whp, and a car that sees more road use than track use, the 6speed and 3.636 is great. the ratios actually matches my local tracks quite good too. but im not using the 6th gear at all on the small local tracks.. if i take the mx5 to the "ring", 6th gear will also be used
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Old 02-27-2010, 08:32 PM   #18
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In Australia our 6 speed MX-5s (including the MSM) all have 3.6 diff ratios and it makes them almost boring to drive!!
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Old 03-03-2010, 07:16 PM   #19
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would not have 3.636 with a stock engine.. i had 4.1 with my 400whp engine, and that was just silly.. spent more time changing gears, than accelerating.. (almost)
3.636 works on very high power cars, or for those just wanting low cruising rpms.
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Old 03-03-2010, 07:42 PM   #20
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Quote:
Originally Posted by hf-mx5t View Post
would not have 3.636 with a stock engine.. i had 4.1 with my 400whp engine, and that was just silly.. spent more time changing gears, than accelerating.. (almost)
3.636 works on very high power cars, or for those just wanting low cruising rpms.
Its pretty easy to look at the 6-speed/3.63 ratios and determine they're slightly shorter in 1-5 than a 5-speed/4.3....then you have the bigger 6th too.

So yes, 6/3.63 is our god except for Savington because he has AIDS.
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