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Old 12-13-2008, 11:33 PM   #1
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Question Transmission and rear gear question

Just kind of a hypothetical question, a "what would you do" kind of thing. While Im purchasing parts and pulling the damn engine what seems like weekly, Id like to maybe go ahead and tackle the trans and rear end while Im at it, to get ready for the turbo. Its a daily driven car that will likely see the BEGi-S with 2554, so not a power monster. I plan to aim for 160-180whp starting out, though it may go a bit north of that, since you can never have enough. Anyway, the options I have set myself are:

-Stock 5 speed with stock (4.1) 3.9 or 3.6 gear
-6 Speed with 3.6 gear

I would really like 6 speed and 3.3, but I cant find a set anywhere, though Ive seen that Richmond might, or was thinking about doing a run of 3.3's. I could stay 5 speed and risk breakage at sub 200whp, and only worry about the rear, if at all. Or I could go ahead and take the safe route and do the 6 speed with the 3.6 gear. The down side to that for me is the fact that you get shorter gears 1-5, and gain the 6 as a kind of cruising gear. The 3.3 would solve this, but as said, dont think it will happen.

Do you think it is worth it to risk running a ~110k mile 5 speed for a reliable daily driver? I really dont want to have to do a trans swap down the road, once its turbo I hope to leave it alone for a while. What would you do? Its either $2000 now for the trans and ring and pinion, or its risking leaving the stock trans in and boosting. My trans seems to be in fair shape, but a little gear noise can be heard, along with an every now and then missed shift. Im quite indecisive when it comes to this kind of choice, so maybe some of you can help me out.

I guess my ultimate question is, should I worry about my current trans at a maximum of 200whp? Or should I save later trouble and go ahead with the 6 speed and 3.6?
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Old 12-14-2008, 01:19 AM   #2
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I'd say that at a max of 200rwhp the 5 speed should be OK. I'm well past that and my 5 speed lasted approximately 500 miles after going FI. I've got the 6 speed with 3.63's now and it's great..............so far.
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Old 12-14-2008, 02:54 AM   #3
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Where do you plan on getting a 3.6? I didn't think they were available anymore. As for the 3.3, I don't think that ever happened either. Not enough people willing to shell out $500 just for the ring and pinion. I am in the same situation you are. I have the 5-speed with a 3.9 (swapped out the 4.3 last year). Now that I finally got my boost stabilized and I am hitting about 12psi, I am starting to hear some gear whine from 2nd and 3rd. 3rd is worse.

However, I know I am eventually going to put a v8 in this thing, so I give you another option. Get the 6speed and the v8roadsters CTS rear diff kit. You can get the 3.42 locking rear on car-part.com for about $250. I think I saw 5 or 6 from the same vendor the last time I was looking. The axles are pretty spendy, but you will never break anything ever. Overkill for just a turbo?? Maybe. But ask how many guys in this forum started out saying "I just want over 200 rwhp". I knew I wanted 250, that's what I have and it still isn't enough.

Funny though, you really get used to the power. I drove a non-turbo 99 today and man was it SLOW.
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Old 12-14-2008, 07:36 AM   #4
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MiataRoadster: Mazdaspeed Motorsports Development parts <--- They have the 3.636 gears apparently.
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Old 12-14-2008, 09:33 PM   #5
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Unless Paul lost a hook-up, MazMart should be able to get the 3.63s (It's were I sourced mine and the speedo gear.)

I'm running the 5-spd / 3.63 combo at 250rwhp and haven't had a problem. But I will caveat the statement noting I don't hammer it in first and WOT in 2nd is *only* for straight lines...

- L
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Old 12-14-2008, 10:06 PM   #6
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If you have trouble later, deal with it later. Stay away from pucked clutches and your 5-speed will be bulletproof at 200whp. Baby your 2-3 shifts and you can make it work at 250+. No need to drop $1000+ into drivetrain parts now.
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Old 12-15-2008, 12:20 AM   #7
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Well thats the thing. Though I may not drive the snot out of it all the time, I still want to have the confidence to do it if I feel like it. The CTS may be an option down the road, but it would have to be a later kind of thing, cause I surely cant spend that right now. Shouldnt the 7'' rear be plenty for a daily driven turbo car at most any power level? Ive only heard of people breaking them at the strip on launches. Only reason I would go CTS and a lower gear would be if I did end up going with 250whp+, like I will probably end up doing. I'll start at 160-180, then I will get bored, and shoot for 220whp, then that will get boring, and then I know 250+ will be the next goal. Can never have enough power Though right now Im wanting it to be a reliable setup, since its my only good car. Once I get another Miata or two, it will be open to more power.

Im running a HD ACT right now, so no pucks here. Hell, maybe I will just stick with fully stock drivetrain for now with the 160-180whp level, and do the 6 speed and CTS crap when I get bored with it, and just go ahead and jump straight to 250-300whp... as long as I dont pound the crap out of it at that power level, do any of you think I will have any issue daily driving it stock? I will of course give in to the occasional red light run, but Ive never felt good launching the Miata since it has such terrible hop. So if I did give it hell, it wouldnt be any kind of hard launch. Most of my commute is interstate, so not much chance to do any stop and go red light racing. Of course I dont support any kind of street racing...

So here is another question. Who here is running 5 speed, how long, and how much power? I just really dont want to run the 5 speed, and have it take a dump at a bad time, and be without my car again for months. If I do the swap, I want to have it planned. But again, maybe at the power I plan to run, it wont be any problem.
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Old 12-15-2008, 12:47 AM   #8
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my 5 speed is keeping the car in the garage in a reasonable manner. However it can't stand this abuse for long, so I have a back up ready for when this one goes. Not sure I would ever upgrade until I either got tired of changing transmissions or got tired of getting stranded
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Old 12-15-2008, 01:07 AM   #9
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Hmmm... well... I dont know if I want to keep spares in case.
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Old 12-15-2008, 01:11 AM   #10
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I picked one up for like $55, so when It goes, I might buy one more, but after that one I will definitely fix the problem and upgrade (with some sort of sequential gearbox )
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Old 12-15-2008, 05:30 AM   #11
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Sequential? Any reason? I see that being a major pain in the ***, and major money pit. But go for it, it would be different.
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Old 12-15-2008, 05:38 AM   #12
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Quote:
Originally Posted by NA6C-Guy View Post
Well thats the thing. Though I may not drive the snot out of it all the time, I still want to have the confidence to do it if I feel like it. The CTS may be an option down the road, but it would have to be a later kind of thing, cause I surely cant spend that right now. Shouldnt the 7'' rear be plenty for a daily driven turbo car at most any power level? Ive only heard of people breaking them at the strip on launches. Only reason I would go CTS and a lower gear would be if I did end up going with 250whp+, like I will probably end up doing. I'll start at 160-180, then I will get bored, and shoot for 220whp, then that will get boring, and then I know 250+ will be the next goal. Can never have enough power Though right now Im wanting it to be a reliable setup, since its my only good car. Once I get another Miata or two, it will be open to more power.
Don't worry about the diff. If you don't launch the car, the 7" is bulletproof, and even if you do launch it, as long as you don't get wheelhop you're fine. What you have to worry about is the tranny, since those do break.

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Im running a HD ACT right now, so no pucks here. Hell, maybe I will just stick with fully stock drivetrain for now with the 160-180whp level, and do the 6 speed and CTS crap when I get bored with it, and just go ahead and jump straight to 250-300whp... as long as I dont pound the crap out of it at that power level, do any of you think I will have any issue daily driving it stock? I will of course give in to the occasional red light run, but Ive never felt good launching the Miata since it has such terrible hop. So if I did give it hell, it wouldnt be any kind of hard launch. Most of my commute is interstate, so not much chance to do any stop and go red light racing. Of course I dont support any kind of street racing...
At 180whp and a street disc, you'd have to work really hard to break a 5-speed. Mine lasted 6,000 miles of clutchdumps and HARD 2-3 shifts before it finally let go on a particularly hard 2-3 heading down a highway onramp. I then had another 5-speed in the car for a few thousand miles before jumping to a 6-speed.

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So here is another question. Who here is running 5 speed, how long, and how much power? I just really dont want to run the 5 speed, and have it take a dump at a bad time, and be without my car again for months. If I do the swap, I want to have it planned. But again, maybe at the power I plan to run, it wont be any problem.
Even if you do FUBAR one, they are cheap and plentiful to replace. I really doubt you'll have an issue at the power levels you want to start out at, though. Until you get up above 250whp with a street disc, the money is probably better spent elsewhere (tires, suspension, brakes, etc).
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Old 12-15-2008, 05:44 AM   #13
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Thanks. Maybe I will just stick with the 5 speed for now, then the next big thing after the turbo will be the 6 speed and 3.6 gear. So it will only have to get me through 4-6 months of fairly spirited to and from work commute, and weekend fun. Shouldnt be an issue though. thanks for the help guys, I guess its stock for now, and down the road the 6 and 3.6 gear.
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Old 12-15-2008, 08:01 AM   #14
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how does the six speed tranny do under a massive load of power do they hold up good?
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Old 12-15-2008, 08:39 AM   #15
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define massive load....


and Savington, you say the 5 speeds are plenty, yet I have trouble locating a decent one for a good price. any suggestions? mine is still OK but 2nd is starting to become a real bitch and I can see it shitting itself once I boost the car.
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Old 12-15-2008, 02:57 PM   #16
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Quote:
Originally Posted by 18psi View Post
define massive load....


and Savington, you say the 5 speeds are plenty, yet I have trouble locating a decent one for a good price. any suggestions? mine is still OK but 2nd is starting to become a real bitch and I can see it shitting itself once I boost the car.
people are always parting out cars on here and selling the 5 speeds for anywhere from $50 to $100, just keep a vigil and you will find one
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Old 12-16-2008, 05:05 AM   #17
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Quote:
Originally Posted by 18psi View Post
define massive load....


and Savington, you say the 5 speeds are plenty, yet I have trouble locating a decent one for a good price. any suggestions? mine is still OK but 2nd is starting to become a real bitch and I can see it shitting itself once I boost the car.
like 22-25 psi over 400 horse a massive load defined lol
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Old 12-16-2008, 05:09 AM   #18
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Quote:
Originally Posted by mazda/nissan View Post
people are always parting out cars on here and selling the 5 speeds for anywhere from $50 to $100, just keep a vigil and you will find one
I'm watching the classifieds like a hawk
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like 22-25 psi over 400 horse a massive load defined lol
on a miata? why?
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Old 12-16-2008, 06:07 AM   #19
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why does every one ask that cause i want a beast and the miata is one of my favorite cars that's why its already making big power but im not stopping there
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Old 12-16-2008, 06:25 AM   #20
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I would never want over 250whp on a street driven Miata. No point really. Ideal for me would be between 160-240whp. Somewhere in the middle. Mix of tons of fun, and reliable. I want it to be easy to drive, easy to take care of, and easy to kick the **** out of cocky Mustang, Camero, T/A drivers, and the funny ricer import kids.
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