Gears for my KK

Discussion in 'KK General Discussion' started by Hunter Toth, Jun 25, 2020.

  1. Hunter Toth

    Hunter Toth Member KJ Supporting Member

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    There is a sticky thread on the gears available for the KK and Diggerfreek mentions that you can get 4.56 and even 4.88 gears in the KK

    I've heard before that the KJ has a max of 4.10 in the front?
    Also, does anybody know when the carrier has to be replaced? I'm only looking at changing gears - not carriers

    I've been running 32"s on 3.73 with a lot of added weight from my mods (full skids, front bumper & winch, steel rear driveshaft, 32" spare, hi-lift, filled jerry can, my tools, and soon a rear bumper) so my mpg is pretty shit

    the main questions is, 4.10s would put me almost exactly on par with the stock revs, but with all the extra weight maybe I should go 4.56s?
     
  2. Homeward_Bound

    Homeward_Bound New Member KJ Supporting Member

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    We have the same diff as the JKD30, so any gear/locker for the JK will fit our front differential. I myself have 4.56 installed with an Eaton locker up front.

    We have a carrier break, but thats for gearing 3.07 and numerically lower iirc so no need for that.

    If you offroad a lot, I'd go 4.56 for the extra torque. At 65mph, I hover around 2250 rpm and get ok gas milage on the highway.
     
  3. lfhoward

    lfhoward Full Access Member

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    Homeward_Bound, what size are your tires? 4.56 would work well with 32’s but I am thinking it might be pretty high revving with 31’s.
     
  4. Homeward_Bound

    Homeward_Bound New Member KJ Supporting Member

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    I'm on 32's, looking to squeeze 33's next time I'm up for tires.
     
  5. Hunter Toth

    Hunter Toth Member KJ Supporting Member

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    ok thanks guys

    so I'm running 265/75/R16s which is about 31.6".
    i do medium offroad fairly often, lets say every other weekend for the whole summer

    but more importantly, i do a lot of driving on trips. my cabin is a 400 mile round trip, so i feel the gas savings would be pretty substaintial

    it struggles pretty hard, especially with added cargo for camping. My cheap code reader is calculating an average of 12-13 mpg highway lol :oops:

    so you guys suggest 4.56s? and how much does the brand/price matter? is there a "best bang for your buck" kind of thing?


    Homeward_Bound, do you run a rear locker too?
     
  6. rotary_powered

    rotary_powered New Member

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    I installed 4.88 gears when I had 31.6"(265/65/18) tires, in preparation for my new 34s (305/70/17). It was a little overgeared on the older tires, but it drove well and was manageable, I would think that 4.56s would suit that size tire well.

    I used Yukon install kits for the front and rear, and yukon front gears. I used Dana's SVL line for the rear diff, it's a more budget option, but I haven't had any issues with it. Only thing to note is that Dana SVL ring gear was not dual drilled (SAE and Metric) it only had the older SAE bolt holes. You can use it in your KK, you just have to buy an install kit for pre 2004/05 29 spline Chrysler 8.25, the SAE bolts will fit through the carrier holes into the ring gear perfectly.

    Are you planning on installing these gears yourself? I did mine myself, and can offer up some tips and knowledge if you need it!

    Also as far as fuel mileage, my average is 10-11 mpg (75%+ city, 25% highway). On pure highway drives with cruise at 75mph, I can about 15-16 mpg
     
  7. Homeward_Bound

    Homeward_Bound New Member KJ Supporting Member

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    No rear locker. As for gears, I went with Yukon. From my understanding Yukon and Revolution gear are made in the same shop, Yukon just having the tighter tolerances. So yes. Price does play a factor because you want good gear mesh. As for other brands, not too sure.

    At 31.5, you're in the middle between 4.10 and 4.56. If you do more highway than offroad, 4.10 might be a better option. Can always increase traction with knobbier tires and lockers.

    But with the 4.56, I drove from a Newark gas station to just outside Buffalo cruising at 65. Almost got 360 miles out of the tank while loaded with luggage and steel accessories. I'll average closer to 300 miles if mostly highway. Stopped recording city milage because it sucks hard.
     
  8. Hunter Toth

    Hunter Toth Member KJ Supporting Member

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    wow! 34s! got any pics?
    how does that front diff and CVs like that?

    Id love the cost of installing them myself, how much work is it? Im working from home right now, so i can have the vehicle down for a while
     
  9. Hunter Toth

    Hunter Toth Member KJ Supporting Member

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    ok sounds like Yukon is the way.
    Thanks!
     
  10. tommudd

    tommudd Moderator Staff Member Moderator

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    If you have never done gears, no matter how long you have , you need experience ( like someone doing them, you handing wrenches etc
     
  11. rotary_powered

    rotary_powered New Member

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    Here's a photo of my most recent trip https://photos.app.goo.gl/5id5FfbJkjG3GWHF6

    The CVs and Diff haven't given me any issues yet, but I did kill a steering rack,

    Doing gears isn't easy, but it also isn't the voodoo nightmare that everyone makes it out to be. You'll need some good tools however. Hardest parts are removing the existing bearings from the carrier and pinion (especially trying to not damage the pinion bearing so you can turn it into a setup bearing), and you need a decent sized vise to hold the carrier in while you torque the bearings. You need a good torque large torque wrench for the ring gear bolts, and a dial or beam torque wrench to measure preload on the pinion. I think the most difficult bit will be crushing the pinion crush sleeve, it takes a ton of torque to get it to begin to crush, especially the rear diff.

    If you have a decent amount of mechanical skills and a good attention to detail it should be possible. It's not a hard process, just requires some problem solving when dealing with stubborn parts without large presses and specialty tools. You also need to be willing to remove the carrier multiple times to try different shims to get the correct backlash and preload
     
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  12. tommudd

    tommudd Moderator Staff Member Moderator

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    Repaired way to many to count of newbies doing their own gears thinking they could do it by them selves
    most hauled in on a wrecker LOL
    and then they were mad at us cause we charged them to do it correctly