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Old 12-25-2007, 09:10 PM   #1
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Default Changing the Diff from 4.1 to 3.6

I recently purchased a 1996 with a Fly'n Miata TC added on. The current mileage is approx 42K. I have driven the car only 70 miles since purchase (from home of seller to my garage). Since I plan to use as a Good Weather car (I have a 95M as my DD) I have not even Titled the car as yet.

My neighbor, also a Miata owner and a great Hobby mechanic, is planning to change the diff on his regular '97 as he needs a new diff. He is going to change from a 4.1 to a 3.6. I do NOT have a NEED to change but thought I would take this opportunity, working side by side, to do the same thing.

I am looking for opinions on the GOOD/BAD of making the change on a turbo Miata. The seller of the car said the car was rated on a dyno as 215 RWHP.

This is ALL new to me - any advice or links to go to would be GREATLY appreciated.
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Old 12-25-2007, 11:50 PM   #2
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Go to a 3.9 with the 5 speed.
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Old 12-26-2007, 12:48 AM   #3
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i'd take a 3.6 rear if i could get one at this point. i have a 3.90 currently with a 5 speed. but i have a 2000lb car with god knows how much power. i would like some more gearing. 1st is almost useless. it's good at like 30% throttle. at least in the winter that is
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Old 12-26-2007, 09:00 PM   #4
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I made the swap to the 3.63s before I put the turbo on the car. - But did so knowing I would need a higher top-end/low-rpms for some of the events I am planning on competing in.

When you consider you are looking at nearly doubling the base HP, dropping the rear ratio by about 12% should help driveability more than harm it.

(Considering you won't really see the benefit of the change prior to spool up...)

- L
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Old 12-26-2007, 09:13 PM   #5
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Quote:
Originally Posted by paul View Post
i'd take a 3.6 rear if i could get one at this point. i have a 3.90 currently with a 5 speed. but i have a 2000lb car with god knows how much power. i would like some more gearing. 1st is almost useless. it's good at like 30% throttle. at least in the winter that is
Paul, we'll see either this week or next one (when I can finally get my car to run) whether you may be closer to your wish.

Rafa
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Old 12-26-2007, 11:03 PM   #6
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Originally Posted by Spaniard View Post
Paul, we'll see either this week or next one (when I can finally get my car to run) whether you may be closer to your wish.

Rafa

sounds good.
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