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Thread: Need to Re-gear

  1. #1
    Fresh Catch Crash284's Avatar
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    Need to Re-gear

    I just entered the JK world. Previously I was running a 05 TJ Rubicon and loved it (sadly retired by another driver).

    I have a 2013 sport with the 6-speed and the 3:21 stock gears; currently running 285/70/17 essentially a 33x11.5 caused a shift in my power band and made my jeep slightly gutless over all. I do plan eventually on running a 35s and possibly 37s but not for at least a few years. I would like overall performance on trials and highway; maintaining my MPG and off-road abilities.

    After speaking to some guys at my local shop they recommended 4:88s. I drove an 08 with the 3.8L, 35s, and 4:88s; it left a bad taste in my mouth with how much foot it took at highway speeds.

    Will I experience the same thing with 4:88s? Would 4:56s be more appropriate?

  2. #2
    Resident Smartass OverlanderJK's Avatar
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    You can't compare the 3.8 to the 3.6. The 3.6 is way better. That being said, have you calibrated your speedo for your current tire size?
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  3. #3
    Old Timer noroad's Avatar
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    Quote Originally Posted by Crash284 View Post
    I just entered the JK world. Previously I was running a 05 TJ Rubicon and loved it (sadly retired by another driver).

    I have a 2013 sport with the 6-speed and the 3:21 stock gears; currently running 285/70/17 essentially a 33x11.5 caused a shift in my power band and made my jeep slightly gutless over all. I do plan eventually on running a 35s and possibly 37s but not for at least a few years. I would like overall performance on trials and highway; maintaining my MPG and off-road abilities.

    After speaking to some guys at my local shop they recommended 4:88s. I drove an 08 with the 3.8L, 35s, and 4:88s; it left a bad taste in my mouth with how much foot it took at highway speeds.

    Will I experience the same thing with 4:88s? Would 4:56s be more appropriate?
    How much foot it took? If you think it took more then why would 4.56 a step down be in the running? Also you have to remember that the 3.6 is a huge improvement in power over the 3.8! I guess before regearing you might want to think about what your target tire size is. I run a 3.6 6 speed with 4.88 and like it a ton as it is my DD, i also drove 37 on it with 3.21s and it sucked but was only for a sort time.

    here is what i would do for a couple of things as you have a 3.6 6 speed (depending on what size tire you want)

    33s with daily driver 4.10s
    33s with more rock crawling 4.56s
    35s with dd 4.56
    35s with more rock crawling/ wheeling 4.88s
    37s with dd 4.88s
    37s with more wheeling 5.13s(and a 44 front end)
    Last edited by noroad; 01-19-2015 at 08:43 PM.

  4. #4
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    Quote Originally Posted by OverlanderJK View Post
    You can't compare the 3.8 to the 3.6. The 3.6 is way better. That being said, have you calibrated your speedo for your current tire size?
    AGREED!

    Our 3.8L 2-door with 4.88s and 35s is a dog compared to our 3.6L'd 4-door on stock 4.10s with 37s.


    Since you are waivering on 35s or 37s (currently 33s) and want decent highway use (assuming faster than 70). I would say 4.88s. Any bigger will make for a tiny pinion on the D30 up front.

  5. #5
    Administrator wayoflife's Avatar
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    Quote Originally Posted by Crash284 View Post
    I have a 2013 sport with the 6-speed and the 3:21 stock gears; currently running 285/70/17 essentially a 33x11.5 caused a shift in my power band and made my jeep slightly gutless over all. I do plan eventually on running a 35s and possibly 37s but not for at least a few years. I would like overall performance on trials and highway; maintaining my MPG and off-road abilities.
    So that's it isn't missed, your 285/70R17's that have a true measurement of about 33" is what a tire with 35" stated on the sidewall measures. In other words, you're feeling a considerable power drain because you ALREADY are running a 35" tire and with 3.21 gears.

    After speaking to some guys at my local shop they recommended 4:88s. I drove an 08 with the 3.8L, 35s, and 4:88s; it left a bad taste in my mouth with how much foot it took at highway speeds.
    4.88 will bring you back up to something similar to stock performance plus an extra boost. As mentioned, a 3.8L is a dog compared to a 3.6L motor.

    Will I experience the same thing with 4:88s? Would 4:56s be more appropriate?
    4.56 will give you LESS power. 4.88 is what you'd want with a set of 35" tires that have a true measurement of about 33".

  6. #6
    Fresh Catch Crash284's Avatar
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    Quote Originally Posted by wayoflife View Post
    So that's it isn't missed, your 285/70R17's that have a true measurement of about 33" is what a tire with 35" stated on the sidewall measures. In other words, you're feeling a considerable power drain because you ALREADY are running a 35" tire and with 3.21 gears.



    4.88 will bring you back up to something similar to stock performance plus an extra boost. As mentioned, a 3.8L is a dog compared to a 3.6L motor.



    4.56 will give you LESS power. 4.88 is what you'd want with a set of 35" tires that have a true measurement of about 33".

    Thank you, that's exactly what I was looking for! Also thank you to everyone else that commented, it is much appreciated. Ill go 4:88s

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