Has anyone broken a 6 speed Gearbox here in NZ?

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REDBEN
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Has anyone broken a 6 speed Gearbox here in NZ?

Post by REDBEN » Wed Apr 10, 2013 5:34 pm

I'm just trying to gauge weather I change to an FC RX7 Turbo gearbox or try the 6 speed? There will be a considerable amount of Hp going through it (350+) and I would rather do it once do it right whiles all the gear is out of the car.

Mad Kiwi
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Post by Mad Kiwi » Wed Apr 10, 2013 10:28 pm

Hi Redben, I have studied this hard at Miata turbo and they have pretty much decided the mx5 6 speed can handle up to 450 hp in a race car all day and probably a lot more. I am pretty sure they are yet to see a failure un related to other circumstances i.e. not power related.

They are pretty finicky about the oil they use (notchy) and the one I put in certainly took 3 months or so of use (I believe it had sat for a year or so prior) before the 3rd gear synchro started to semi behave. It still was slightly graunchy, especially cold which is when I researched the oil M Turbo users recommend and other than a dealer in christchurch couldn't find a local source for any of the brands/types suggested.....

In desperation I changed my oil thinking a flush after sitting so long might help and lo and behold either the flush or the Penrite Semi Synthetic 75w90 "mostly" resolved the issue......

Something about "too" slippery oils not allowing the synchros to work properly (something I also experienced on my MX bike...Motul Transoil Great!! - Motul TransOil PRO - Terrible!!).

I like my gearbox now....hated it at first.

Anyway, thought this might help.

REDBEN
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Post by REDBEN » Wed Apr 10, 2013 10:47 pm

Awesome thanks Mad Kiwi, good to know 450Hp should be able to handle it then! Thanks for your help, decision made :D now to find a 6 speed!

last_resort14
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Post by last_resort14 » Thu Apr 11, 2013 2:33 am

Yea, i also did a bit of research on these before i got mine.

The only failures i could find online were usually related to hard downchanging on pretty serious race cars.

Ive been running miine for a couple years now, giving it a pretty hard life, plenty of 4th gear clutch kicks etc, with no issues as of yet. dont know how much power i have, maybe 230hp, and i only run 195/50 street tires.

Ive given it a few oil changes in its time, i use castrol VMX, havent really had any issues, my gear changes arent amazingly fast, and have heard using a thinner oil might be the fix, but it hasnt been enough of an issue for me to bother.

Furai
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Post by Furai » Thu Apr 11, 2013 7:17 am

Yeah I heard the 6 Speed was a bit notchy when I put mine in but upshifts are just as good if not better than the 5 speed. Only thing I find different is you have to always rev match for smooth downshifts.

Im using Valvoline VMX 75W-90 and its quiet and does great even flat shifting with a clutch kick 2nd-3rd and 1st-2nd. Thats with maybe 70whp though :lol:

REDBEN
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Post by REDBEN » Thu Apr 11, 2013 7:18 am

Sweet thanks Luke! If they can survive the abuse of drifting they must be rather strong then.

Furai
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Post by Furai » Thu Apr 11, 2013 7:24 am

Also ask Keith as I think he has blown a few boxes, I dont know which type though.

Mad Kiwi
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Post by Mad Kiwi » Thu Apr 11, 2013 11:28 am

I talked to Keith about this, he had a couple of big issues with 5 speeds letting go.

He went to Quaife as the 6 speeds were an unknown quantity then.

Kieran
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Post by Kieran » Thu Apr 11, 2013 1:21 pm

you'd have to fail like chris to break a 6speed unless your pushing 450+hp

Only problem with the 6speeds is that they are very moody some days they just don't feel like shifting smoothly then the next day like butter

REDBEN
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Post by REDBEN » Thu Apr 11, 2013 1:26 pm

Mad Kiwi wrote:I talked to Keith about this, he had a couple of big issues with 5 speeds letting go.

He went to Quaife as the 6 speeds were an unknown quantity then.
I'd love a Quaife gear set but don't quite have a spare 12k+ 😥

chris
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Post by chris » Thu Apr 11, 2013 2:32 pm

Kieran wrote:you'd have to fail like chris to break a 6speed unless your pushing 450+hp

Only problem with the 6speeds is that they are very moody some days they just don't feel like shifting smoothly then the next day like butter
I didn't even post in this thread?!?!?1 WTFFF

6 speed should be sweet :)
1 X Primera
2 X Silvia
1 X BMW E30
1 X Audi A6
3 X Mazda MX5 (1989, 1990, 1991)

Kieran
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Post by Kieran » Thu Apr 11, 2013 3:12 pm

I know but I like including you :lol:

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