How to Choose Your Axle Gear Ratio – Kansas City Trailer Repair – By

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In this video, I discuss some of the reasons to change your axle gears, as well as a formula to calculate the best gear ratio based on your tire size. All the parts you’ll need to regear front and rear axles:


*This product is meant for entertainment purposes only. Your mileage may vary. Do not try this at home. Void where prohibited. Some assembly required. For off-road use only. Slippery when wet. Batteries not included. Do not use while operating a motor vehicle, heavy equipment, cherokee XJ, wrangler TJ, wrangler JK, or any Jeep vehicle, especially the newer Fiat ones. How-to videos may be too intense for some viewers and children under 30 years of age. Please remain seated until the 4×4 ride has come to a complete stop. Studies have shown viewing these videos causes increased cancer risks in laboratory test people. I am not a professional, I have no training, I’m not even particularly good at horse whispering. Don’t believe everything that you know. Please keep your hands in the vehicle at all times. Do not tap on glass. Do not eat anything that has been on the floor for more than 3 days. Keep your hands to yourself. Not to be taken internally. Reproduction strictly prohibited. Driver does not carry cash. Objects in Bleepinjeep mirrors may be farther than they appear.*



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48 Replies to “How to Choose Your Axle Gear Ratio – Kansas City Trailer Repair – By”

  1. Yes, helped a lot, thanks ! now, I am changing tire/rim size into my Mustang 2004 , is has 17 inch rims, now I am putting 20 inch rims on it! I am "tuning up" engine, adding supercharger on it, even it is V6, 3.8 litre, and I am thinking changing gear ratio to 3.73?? Should I put 4.10 rear instead?? My car wants to be fast, 0-60…., will not have lots a highway miles. Horsepower we will be looking for 350-400?? And , yes, it is manual transmisson!!! Which one would be better, with big rims/tires?? Thanks, youtheman =)

  2. I have a 87 Chevy V20 diesel 4×4 and my question is do I need to use the same size ring and pinion for front and back and can I order two of the same ring and pinion set and install them into my truck? Note : I have a 10 bolt corporate front and a 14 bolt rear I'm looking to get 3.42 sets but i'm a bit confused because they come in 9.5" and 10.5" for the 14 bolt and the 10 bolt comes in 8.5" and 8.6" !! And another side note I swapped out my TH400hd automatic for a Dodge NV4500 5 speed manual and I still have the stock tires and rims installed

  3. Hey there
    I have a question please i need help
    I have a 2014 sahara with 3.5 lifting and 3.73 gear with a 35" tires and i want to upgrade to 37" tires
    Should i stay with the 3.73 gear or i have to change it? My jeep is my daily driving and i live in Manhattan in the city i Don't do too much off roading but i would like to start this summer, my question is should i regear and if yes what will be the best option for me.
    Thank you

  4. Ok may be a good place to ask this I have a 96 jeep yj all stock but I'm going fix it up know I have the motor for most part but I'm stuck on transmiton, frontend and and rear end any tips on what to pick

  5. I got a question ok so what if I bought my jeep at a auction and It has 33 on it now I stopped at my local jeep otr shop and he told me it has a Dana 44 in the rear but I have no idea what gears it has the jeep is a 2000 jeep wrangler sport 5 speed inline 6 but as for the front I have no idea at all what the original gears was in it so I want to go mudding but until I know my 4×4 is all in great shape I don't want to mess it up I can say the gas mileage is poor bad so you got any suggestions to help me figure all this out thanks

  6. I have an 06 Wrangler Unlimited. The stock tires were 15'' but I swapped them out for some 35'' ones. The gear ratio for that model is listed as 3.73. Problem is, when I calculate the new gear ratio, I get a value of 8.7, which is both absurd and impossible. I had no idea it needed to be changed when equipping larger tires, nor was I told.

    That being said, is it harmful to my Jeep to leave the gear ratio unchanged? Also, what is the proper gear ratio for my setup?

    It's been a couple years since I had the new tires installed and I haven't had any issues. If money grew on trees I would gladly change the GR, but it doesn't. I can't afford something like that in the present time, but even if I could, I am not sure what GR I should convert to.

  7. I have a question. I am wanting to upgrade to 35” tires, and by your formula I should change to 3.73 gears. Most suggest a minimum of 4.10. I’m conflicted on which gear set I should go with. This is an awesome video, thank you.

    2017 wrangler Sahara
    3.21 gears on stock 31” tires

  8. Question : I have a 88 jeep YJ, got it used , came with 31" tires my gear ratio according to the tags are 3.07 Front and rear. Dana 30 and 35. I got a sweet deal on 33" tires. The math says I need 2.88 gears.. I'm thinking that the original owner(s) never re-geared when they put 31" tires on. So should I try and recalculate based on a stock size tire from 1988? Really want to throw these 33" tires on but not if its going to be a really bad idea… Thanks! Great video!!!!!!!

  9. What about the front differential gearing? I have a 2500hd Silverado Duramax with 3.73 gears front and back. Went from 31.5" tires on 20" rims to 35" tires on 22" rims.
    Per your equation I should be running 4.10 gears In the rear end i believe.
    But what should I do about the front end differential?? Bleepinjeep

  10. I must have done something wrong because 4.56 gears will not work with 37 tires. I have those gears on my 5 speed TJ with 33’s. My new to me LJ has 3.73 with 31’s and I want 37’s. I’m no mathematical genius but I came up wit 4.56 gears knowing I will need something like a 5.13 with the 6 speed transmission. Either my math is off or this guy is blowing smoke. Please help.

  11. Yup just swapped to 30inch tires for winter and noticed on the highway it’s hard for my Jeep to find a gear between 65 and 70 during the summer I have 32 inch tires so now gotta watch more for my ratio need

  12. I had absolutely no use for this information, BUT this was one of the best informational/educational videos I've ever seen!!! Great Job. I am confident that I'm now proficient in the science of gear/rear-end ratios and set up. This dude is brilliant in his simplistic presentation of info! Thank you sir.

  13. Wow' i never realized what was taking place under neath, and here's me thinking just because I changed oil' a few flat tires, air filter and a couple of headlights I thought I was all that' "ha, very helpful video, keep up the good work.

  14. Can you figure new tire size after a gear swap? I got a 94 s10 that had 3.42 gears and i swapped a zr2 axle onto it with 3.73 gears. I've been wondering what size tires I can use and keep the AT happy.

  15. I bought a 2000 Dodge Dakota 4×4. When I shift into 4WD the passenger side rear wheel will spin in a forward direction a little bit faster than my front wheels. I am thinking that the rear axle was changed at some point but has the wrong gear ratio. Or maybe the transmission was swapped out at some point and the new transmission has a different ratio. So how do I determin the correct ratio for my rear axle. How do I match the ratio of my rear axle with my transmission

  16. Can you tell me pls what should I run gear to my 99 jeep tj 2inch lift 32 tires Dana 30 in front 35 in rear and what locker should I get? Dana’s 30 and 35 is stock I’m not sure what gear in there!

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