5spd + 4.10 torsen or 6spd + 3.636 clutch lsd? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-13-2008, 09:09 PM   #1
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Default 5spd + 4.10 torsen or 6spd + 3.636 clutch lsd?

Have been planning on just putting the 5 spd and 4.10 Torsen I have here into the project car. Because I already have them sitting here and they'll do the job.

But now I'm thinking about selling the 5spd and the Torsen and putting the proceeds toward a 6spd, an rx7 clutch lsd, and a 3.636 ring & pinion set.

If I stay with the 5spd, I'd go with a 2560 for sure. If I go with the 6spd, though, I'd be mighty tempted to go with a 2860.

The real motivation here is that I'm thinking about the health (and value) of this Torsen. If I use it in the turbo project and it breaks, it's worthless. If I sell it and go with an rx7 clutch-type diff, I have a rebuildable diff and no worries about wrecking a Torsen.

Thoughts?
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Old 11-13-2008, 09:24 PM   #2
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Even if it broke beyond repair, clutch types are $100 or less.
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Old 11-13-2008, 09:27 PM   #3
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I am actually having to make this same decision as well....Ill be watching this thread
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Old 11-13-2008, 09:28 PM   #4
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+1 to what he said.

I'm personally going with a 6-speed and 3.636 gears right now. Coupled with my Cusco LSD. And if you decide to go that route, might as well go with a 2871. It's the upgrade for the 2860 (same turbine, larger compressor wheel, 71mm/56trim compared to 60mm/62trim), around the same cost, makes better power more efficiently.
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Old 11-13-2008, 09:49 PM   #5
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One thing that might help me make up my mind- what's a reasonable asking price for a 75k mile Type 2 Torsen these days?
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Old 11-13-2008, 09:54 PM   #6
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Torsens in the carrier sell for $450-500 pretty commonly for some reason.
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Old 11-13-2008, 11:04 PM   #7
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Quote:
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Even if it broke beyond repair, clutch types are $100 or less.
I don't understand your statement. Could you please clarify what you mean?

Thanks
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Old 11-14-2008, 02:21 AM   #8
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Torsens range from 400-500 in used form so if you break one you're out 400-500 bucks. If you break a clutch type(which you can't really, they just slip and need rebuilt) they are only $100 to replace in complete form minus whatever you need to get it preloaded correctly.
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Old 11-14-2008, 02:35 AM   #9
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Bottom line - you'll break the 5-speed eventually, and the Rx7 is stronger than the Torsen. The 5-speed and the Torsen are nicer parts to drive, but the 6-speed and Rx7 LSD are better on track and stronger.
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Old 11-14-2008, 10:42 AM   #10
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you're **** is going to blow up and chop your feet off.

I wish I could find a 6-speed.
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Old 11-14-2008, 11:48 AM   #11
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I have a related question based on this discussion. I am about to change the diff gearing from 4.30 (stock '99) to 3.636. This should reduce the torque load on the differential due to the reduced torque multiplication at the carrier, about a 15% reduction based on the ratio change.

Taking that into consideration, does that in the experience of those here reduce the torsen load enough to reduce the risk of failure within the torsen itself? In other words, have people still managed to 'easily' explode torsens with 3.6 gears? Was it drag racing at 18 psi, or in a daily driver? In my case it is for a street car with 205 street tires, and a 1.8L running 12psi (15 psi max) boost; am I OK if I do not drive the crap out of it all the time?

I ask because I am about to install the 3.6 gears and if my torsen is at great risk, then maybe I should consider the rx7 option. Since the torsen is worth as much as $400, it would be best to sell it while it is still good as mentioned above, and use the proceeds to pay for the swap parts. I do like the torsen so if it will probably be OK I'll keep it.
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Old 11-14-2008, 01:03 PM   #12
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I've been running a 3.9 RX-7 LSD in my SC'd track car for over 2 years. The car makes ~200 RWHP at the ground. I went to a taller tire this year in hopes of achieving higher max speeds on track.

I found that the taller tire (225/50/15 vs 225/50/15) hurt my ability to accelerate. ( I have traqmate) That's because the longer lever arm reduced the amount tire drive force available to accelerate the car down the track. I would think the 3.6 gearing would have a similar effect.

I just busted a tranny recently and was considering a 6 speed. Here's what didn't appeal to me. With the 6 speed, you would use 3rd gear in place of 2nd on the 5 speed. 2nd gear in my 5 speed was really torqy and powerful for blasting through/out of slow tight corners. I don't think the gearing of the 6 speed 3rd gear would provide as much power and 2nd gear would probably have you bouncing off the rev limiter before you could do anything with it.

Unless you're making power at level of 250 RWHP or more, I'd think hard about going to a 3.6 rear end. Just my $.02 worth, YMMV.
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Old 11-14-2008, 01:10 PM   #13
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in for t-56 swap kit.

I'm really not looking forward to blowing up transmissions constantly. We need someone other than quaife to make a gearbox.
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Old 11-14-2008, 01:17 PM   #14
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Quote:
Originally Posted by rrroadster View Post
Unless you're making power at level of 250 RWHP or more, I'd think hard about going to a 3.6 rear end. Just my $.02 worth, YMMV.
FWIW I can't speak to the OP, but personally I am doing it since my car does lots of highway miles daily at 70-80 MPH. The lower RPM will be nice. Plus I want to somewhat alleviate the mostly useless first gear syndrome. I do not plan to track the car (autox, drag, or road), at least not regularly, so that is not a big deal for me.
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Old 11-14-2008, 03:37 PM   #15
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Quote:
Originally Posted by rrroadster View Post

I just busted a tranny recently and was considering a 6 speed. Here's what didn't appeal to me. With the 6 speed, you would use 3rd gear in place of 2nd on the 5 speed. 2nd gear in my 5 speed was really torqy and powerful for blasting through/out of slow tight corners. I don't think the gearing of the 6 speed 3rd gear would provide as much power and 2nd gear would probably have you bouncing off the rev limiter before you could do anything with it.
I've had my car at three tracks. Big Willow, Thunderhill and Buttonwillow.

Thunderhill has three possible 2nd gear corners. 5, 12, and 14. I use 3rd in all of them, for different reasons (the 2-3 after 5 is on a downhill off-camber high-load corner and it upsets the car, and 12 and 14 are juuust fast enough to make 2nd a waste of time with 200tq). That was with the 5-speed; I don't think I've been to t-hill with the 6.

Buttonwillow only has one corner that's worth going down to 2nd on, and with 3rd in the 6-speed it's perfect. It tows nice and hard out of the corner and I grab 4th just as I'm straightening the car out.

Willow doesn't apply, I drop down to 4th for one small complex and the rest of the track is 5th and 6th. Very fast.

At least with the 4.1, the 6 acts like a 5-speed with a long 2nd; 3rd only runs out to about 70mph and it's nice to have that little bit more rev when you're coming off tight corners. For autocross, my 2nd gear is a monster and I have more tow out of tight showcases and hairpins than any other Miata out there.
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