Thread: Gear Ratios

  1. #1
    Join Date
    Dec 1999
    Location
    Virginia Beach VA
    Posts
    8,116

    Gear Ratio Calculator

    Gear Ratio Calculator


    This simple Gear Ratio calculator assumes that you're running around 65 MPH


    All you need to do is look at your tire size on the left, then find out how many RPMs your engine is at when you are doing 65 MPH, and that will give you your Gear Ratio. the blue blocks are good gas mileage, green it a good medium and red is for more power.



    Gear Ratio
    This chart will tell you the rpm needed to reach 65 mph


    Tire
    Size









    3.31 3.42 3.55 3.73 3.91 4.11 4.27 4.56 4.88 5.13 5.29 5.38 5.71

    27


    2677 2766 2872 3017 3163 3325 3454 3689 3947 4150 4279 4352 4619

    28


    2582 2668 2769 2909 3050 3206 3331 3557 3806 4001 4126 4196 4454

    29


    2493 2576 2674 2809 2945 3095 3216 3434 3675 3863 3984 4052 4300

    30


    2410 2490 2584 2715 2846 2992 3109 3320 3553 3735 3851 3917 4157

    31


    2332 2409 2501 2628 2755 2896 3008 3213 3838 3614 3727 3790 4023

    32


    2259 2334 2423 2546 2696 2805 2914 3112 3331 3501 3610 3672 3897

    33


    2191 2263 2349 2469 2588 2720 2826 3018 3230 3395 3501 3561 3779

    34


    2126 2197 2280 2396 2512 2640 2743 2929 3135 3295 3398 3456 3668

    35


    2065 2134 2215 2328 2440 2565 2664 2845 3045 3201 3301 3357 3563

    36


    2008 2075 2154 2263 2372 2493 2590 2766 2961 3112 3209 3264 3464

    37


    1954 2019 2095 2203 2308 2426 2520 2692 2881 3028 3123 3176 3370

    38


    1902 1966 2040 2144 2247 2362 2454 2621 2805 2948 3040 3092 3282

    39


    1854 1915 1988 2089 2190 2302 2391 2554 2733 2873 2962 3013 3198

    40


    1807 1867 1938 2037 2135 2244 2331 2490 2664 2801 2888 2937 3118

    41


    1763 1822 1891 1987 2083 2189 2275 2429 2599 2733 2818 2866 3042

    42


    1721 1778 1846 1940 2033 2137 2220 2371 2538 2668 2751 2798 2969

    43


    1681 1737 1803 1894 1986 2087 2169 2316 2479 2606 2687 2733 2900

    44


    1643 1698 1762 1851 1941 2040 2119 2263 2422 2546 2626 2670 2834



    Blue = 2600 RPM

    Better Mileage

    Green = 2800 RPM
    Around factory

    Red = 3100
    RPM
    Good Power

    Last edited by TerryMason; 03-30-2014 at 01:33 PM.

  2. Re: Jeep Gear Ratio Calculator

    Terry,

    Should I assume I am driving in 5th gear to reach 65mph, please confirm the gear.
    Last edited by TerryMason; 07-20-2009 at 07:27 AM.

  3. #3
    Join Date
    Aug 2009
    Location
    Newfoundland, Canada
    Posts
    165

    Re: Gear Ratios

    i have a four cyl jeep and i put a 4 inch lift and 35 inch tires my jeep cant go fast enough to put her in 5th gear i drive aeround in 3rd and 4th gear and she can only do 100 km/h.. i want my jeep to go faster and have more power for in the mud and in sand.. can u plz tell me what to do with my jeep

  4. #4

    Re: Gear Ratios

    Quote Originally Posted by captjanes View Post
    i have a four cyl jeep and i put a 4 inch lift and 35 inch tires my jeep cant go fast enough to put her in 5th gear i drive aeround in 3rd and 4th gear and she can only do 100 km/h.. i want my jeep to go faster and have more power for in the mud and in sand.. can u plz tell me what to do with my jeep
    Regear the axles to 4.88, that is as low as you can go with the stock axles, even though lower is better.

  5. #5

    Re: Jeep Gear Ratio Calculator

    Quote Originally Posted by kawstxf15 View Post
    Terry,

    Should I assume I am driving in 5th gear to reach 65mph, please confirm the gear.
    I think it would be 4th, or 1:1 transmission ratio.

    Regardless of transmission gear, find your stock gear ratio on top and move down until your at your stock tire size. Record that RPM. Then move to your current or desired tire size and move across the chart to the right until you find an RPM similar to the previous number. Move up and find the suggested gear ratio for the new tire size.

  6. #6
    Join Date
    Aug 2009
    Location
    Newfoundland, Canada
    Posts
    165

    Re: Gear Ratios

    so what ur saying is that to get more speed and power out of my jeep i has to change the gears in the front and rear differentials axels? someone told me that i had to change a gear in the transmission is this true or do i just have to regear the axels? and can u tell me how about going to regear the axles.. where can i order gears to? thanks in advanced

  7. #7

    Re: Gear Ratios

    Hello to terry mason.. I have been looking into 4:88 gears and have found that your chart is wrong 31" tires and 4:88 gears you have 3838 and it should be 3438 thanks team twisted off road.

  8. #8

    Re: Gear Ratios

    Quote Originally Posted by Team Twisted Off Road View Post
    Hello to terry mason.. I have been looking into 4:88 gears and have found that your chart is wrong 31" tires and 4:88 gears you have 3838 and it should be 3438 thanks team twisted off road.
    It's all relative to what gear the transmission is in, and isn't really necessary information to use the chart.

    To simply use the chart, find the given RPM for stock tire size and stock gear ratio. Then go the line of the tire you want to run, and move over until you find a similar RPM, or slightly higher, that is your recommended gear ratio.

  9. #9

    Re: Gear Ratios

    Quote Originally Posted by bounty__hunter View Post
    it's all relative to what gear the transmission is in, and isn't really necessary information to use the chart.

    To simply use the chart, find the given rpm for stock tire size and stock gear ratio. Then go the line of the tire you want to run, and move over until you find a similar rpm, or slightly higher, that is your recommended gear ratio.

    Gear Ratios-gear_ratios.jpg

  10. #10
    Join Date
    Mar 2006
    Location
    Denver, Colorado
    Posts
    312

    Re: Gear Ratios

    I have found this program to be very helpful when trying to figure out crawl speeds, ratios, rpms etc.

    Gear Ratio Calculator

    Bacon

  11. #11

    Re: Jeep Gear Ratio Calculator

    I am new. In what gear? I have 5 speed manual, 4 cylinder with 35" tires. I think the previous owner put the big tires on to look cool without thinking about the effects it would have on performance. Any of your suggestions will be highly regarded. Thanks in advance for the help.

  12. #12

    Re: Gear Ratios

    Welcome to the Z. 4.88 is as low as you can go with the stock axles, so that's your best choice.

    I run a 2.5L 5spd and 35" tires, 5.38 gears work perfect for me but I had to upgrade to Dana 44 axles.

  13. #13

    Re: Gear Ratios

    Thanks Bounty_Hunter

  14. #14

    Re: Gear Ratios

    '87 Comanche 4x4 lifted 5 1/2" on 33" tires 4.0L/AW4/NP242 $3500
    Perfect combination but too small to haul my Grand Kids and wife in.


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