What broke on your 6 speed? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-12-2013, 10:06 PM   #1
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Default What broke on your 6 speed?

After some reading it looks like quite a few of the 6 speeds have failed while in 4th gear. The thing is, mine will never see 4th. The 5spd finally gave up and so the consideration is taking out the 3.63s and going back to the 4.10s and use 3rd gear in the 6spd. Currently 245lb/ft of torque on a mustang dyno but considering some engine upgrades as well. The other consideration is a TKO 500 or Jerico, but that's at least a $4000 project. Thoughts?
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Old 09-12-2013, 10:11 PM   #2
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I'll buy the 3.63's to help knock a few bucks off that total cost.
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Old 09-12-2013, 10:24 PM   #3
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Not if I do first.
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Old 09-13-2013, 01:34 AM   #4
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All the 6-speeds I've heard of breaking have been 4th gear under power.
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Old 09-13-2013, 03:28 AM   #5
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Shift from third to fifth, unbreakable transmission.
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Old 09-13-2013, 03:48 AM   #6
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5th gear is win gear
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Old 09-13-2013, 08:51 AM   #7
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Thanks for the completely useless suggestions to use 5th gear.
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Old 09-13-2013, 09:54 AM   #8
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Broke the 5/R shift fork.
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Old 09-13-2013, 10:20 AM   #9
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Quote:
Originally Posted by guttedmiata View Post
Thanks for the relatively useless suggestions to use 5th gear.
FTFY

I find fifth gear quite useful when 4th gear isn't enough and 6th gear is just a bit too much.
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Old 09-13-2013, 07:38 PM   #10
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Quote:
Originally Posted by fooger03 View Post
FTFY

I find fifth gear quite useful when 4th gear isn't enough and 6th gear is just a bit too much.
It's a dedicated autocross car. Kindly read the original post and replace your relatively with completely. Thank you.
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Old 09-13-2013, 09:22 PM   #11
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I've heard of a few people running little over 400whp with a 6spd w/o problems, but then again they aren't hardcore autoXers.

I have a car with 280whp and 249ft/lbs and the same stock 5spd trans for 6ish years now I believe, couple clutches but who's counting.
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Old 09-13-2013, 11:35 PM   #12
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Quote:
Originally Posted by guttedmiata View Post
Thanks for the completely useless suggestions to use 5th gear.
I'm really sorry you didn't like the suggestions.

I'm gutted.
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Old 09-14-2013, 02:58 AM   #13
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Quote:
Originally Posted by Raucky View Post
I have a car with 280whp and 249ft/lbs and the same stock 5spd trans for 6ish years now I believe, couple clutches but who's counting.
You're living on borrowed time.

--Ian
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Old 09-14-2013, 10:04 AM   #14
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I'm convinced at this point that how long the 5spd lasts behind power is relative to tires and gearing. We went two seasons at about 200whp and one season at 275whp with the 5 speed but could light up the tires by breathing on the throttle. Then we went to the 3.63 rear for traction purposes. In addition to traction, a higher gear is also going to create more load on the driveline in general. The tranny only lasted one and a half events after the change. Poor little guy.
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Old 09-16-2013, 02:53 PM   #15
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Were it turbo, I'd say run less boost in low gear.

Even so, couldn't you use gear dependant timing or fuel, etc, to keep yourself in traction, instead of over-gearing the car? Just a thought.

My 5 speed also long outlived any expectations, when it did go: I hit a bump during a shift. Interesting about the 6 speeds though...
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Old 09-17-2013, 04:41 PM   #16
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FYI, the S15 Silvia and IS200 use the same Aisin AZ6 that came in the Miata. The S15 guys in particular have a fair amount of empirical data about the failures in their gearboxes since 300+whp SR20s are not uncommon overseas. They seem to have similar issues at similar power levels - good reliability at 300whp, mediocre at 350whp, borrowed time at 400+whp.
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Old 09-17-2013, 05:33 PM   #17
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Quote:
Originally Posted by M.Adamovits View Post
Broke the 5/R shift fork.
me too! 2-3 weeks ago
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Old 09-17-2013, 05:51 PM   #18
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I bent a 5/R shift fork a few years ago in my first 6-speed, but I'm pretty sure it had something to do with my attempt to find reverse gear instead of 6th gear...from the top of 5th.
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Old 09-17-2013, 05:55 PM   #19
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Had the go into reverse issue. Never thought of this before, but there isn't any aftermarket reverse lockout thing, is there? I know it's common, not sure if anyone has externally implemented it.
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Old 09-17-2013, 06:06 PM   #20
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Mine was caused by a seating position change. I got used to it and never had another issue.
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