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Thread: 3.63 differential

  1. #1
    Original Gearhead Joe Morreale's Avatar
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    3.63 differential

    Especially since I turboed the Frog I've though about changing from the 3.9 diff to a 3.63. It's what they put in European Mazdaspeeds. I think it'll be a little slower accelerating but sixth would be a real overdrive. At 80 mph motor runs about 3500 rpm. That's about 500 rpm less than what I have now. I think I can get a decent price on it and I have some toy money saved. One of these days I'm going to get a forged motor, so I'll have the ideal setup. I'd like to have 250whp, or in that range, if I can ever scrape up enough dough. In the meantime I'll resist the urge to turn it up over 200whp.
    2001 SE British Racing Green - FM frame rails - FM solid sway bar - FM clutch- Mishimoto 53mm radiator - Bilsteins -
    Complete MK Turbo kit with intercooler - 3'' custom exhaust - Custom door panels - Custom "shorty" console

  2. #2
    Original Gearhead pdexta's Avatar
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    Re: 3.63 differential

    I always struggle picking a rearend ratio. It'd be nice if you could test a few out before committing.

    At least you have a plug and play oem option, and there should be plenty of demand for the old 3.90 torsen if you want to recoup some investment. Or just hang on to both for a while, I think we've reached a point that oem miata parts won't be going down in price...

    The more I write, this is turning into a sound financial investment rather than pissing away money on a toy. If anyone needs financial advise let me know, I'm always happy to help justify the car parts you would like to purchase.
    Scott
    2001 Honda S2000 ♦ 6sp
    2005 Civic Hybrid ♦ 5sp

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  4. #3
    Individual-1 ☚☻☛ Agent☣Orange's Avatar
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    Re: 3.63 differential

    I'd hold on to that S2000. That's for sure.

  5. #4
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    Re: 3.63 differential

    well I have had my 3.63 diff in my turbo car for over a year now.

    *edit* its been 2.5 yrs!

    I have a 1.6, so keep that in mind

    It is great being able to use 1st gear across an entire intersection! You really get to use each gear for a while. The turbo does start making boost a lot earlier as well, so that is a bonus.

    the downside for me is that I have a 1.6, and it just lacks that 20 or so ft lbs of torque before the turbo kicks in to make it enjoyable in stoplight traffic. I am certain this would be non existent in your vvt car, as they have a lot more torque that a standard 1.8 car.

    For reference, our typical spec miata motors on the dyno avg as such - 1.6 100-105 ft lbs, 99/00 114-118 ft lbs, 01/05 118-122 ft lbs

    since the 3.63 diff was only offered in the vvt cars overseas, it does make sense it would work better in that application

    Now I drove Joshua's 1.6 car with the 3.9 diff and it was about perfect IMHO. So I am hoping to duplicate that with a 3.9 diff I got sitting on the floor from a spec miata donor car that I got through work.

    Finding a 3.63 torsen is tough, as most of those cars got the fugi diff in it. I bought mine with the fugi, which had a bunch of broken tabs in it, so I bought a torsen and swapped it over. I didn't trust it, even if the intrawebs said it would be fine. I track this car on occasion and didn't want to have differential problems at a bad time.

    Joe, if you decide to pull the trigger on the diff swap, I will be glad to help out. I think I still have a thread saved for ordering the correct speedo gear too.

    -jason

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  7. #5
    Original Gearhead Joe Morreale's Avatar
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    Re: 3.63 differential

    Having your help would be great. I've been reading on how to replace the whole diff and it doesn't sound outside of my abilities, but by myself would take forever. Just give me at least a couple days heads up and I'll be ready anytime.
    Everything I've read about 1.8 turbo cars is they are happy with the 3.63 gear. Did Joshua ever figure out what kept breaking his motors?
    2001 SE British Racing Green - FM frame rails - FM solid sway bar - FM clutch- Mishimoto 53mm radiator - Bilsteins -
    Complete MK Turbo kit with intercooler - 3'' custom exhaust - Custom door panels - Custom "shorty" console

  8. #6
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    Re: 3.63 differential

    I swapped in the 3.9 diff friday evening when I got home after work. So much easier now that I have a lift here!

    I really enjoy driving it now - the car just feels more balanced which is what I was after.

    If you decided to buy my diff, I will do the install. It should take about an hour and a half. Just depends on how long to remove the exhaust honestly. The rest of it is pretty straight forward.

    Joshua was having issues with the rings - seems to be sorted out now, but he hasn't put any miles on it for other reasons.

  9. #7
    Original Gearhead Joe Morreale's Avatar
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    Re: 3.63 differential

    I have v bands holding my exhaust. Comes off in ten minutes. Text me how much you want and when you might be able to do it.
    2001 SE British Racing Green - FM frame rails - FM solid sway bar - FM clutch- Mishimoto 53mm radiator - Bilsteins -
    Complete MK Turbo kit with intercooler - 3'' custom exhaust - Custom door panels - Custom "shorty" console

  10. #8
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    Re: 3.63 differential

    test message sent

  11. #9
    Original Gearhead Joe Morreale's Avatar
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    Re: 3.63 differential

    Went to Jason's yesterday. After letting it cool, started out by draining the old fluid. Uh oh. Why is there a spring stuck to my drain plug. Looks like my 3.9 torsen was going to grenade itself sometime in the future. It took about an hour and a half to swap the whole diff out. That included farting with a chassis brace bolt that the internal nut spun.

    Driving with the new diff is sweet. Gears run out a little bit farther. 80mph cruising is at 3750 rpms. My only issue is I have to tweak the exhaust. It hits the chassis on deceleration. Not that I'm looking for a gas miser but, I have to go to Kissimmee this weekend. It will be interesting to see if I get better gas mileage. Final note, if you have a fi car this is the diff you want.
    2001 SE British Racing Green - FM frame rails - FM solid sway bar - FM clutch- Mishimoto 53mm radiator - Bilsteins -
    Complete MK Turbo kit with intercooler - 3'' custom exhaust - Custom door panels - Custom "shorty" console

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  13. #10
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    Re: 3.63 differential

    I am glad that you are happy with it. I knew it would be a great match for your car.

    Bonus that the speedo is accurate now!

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