regearing a KJ

    ok, ok...stop laughing!


    When we got our KJ with its tiny little P215/75R16 tires and the V6, it was really fast. Now that we have 31's, its not so quick anymore. Can I change the gears in the rear to get some of that back? Its a "Corporate 8.25" and I think its a 3.73. What would I be gaining? What would I be losing? I see the gears are not too expensive, but I know nothing in this area. Seems like everyone changes gears like its easy, so thought I'd ask.


    When you stop laughing about regearing a Liberty, let me know what's possible.



    Thanks!


    DrJ (will probably regret posting this...)

    i was thinking of regearing my Tj and i looked at the gears and they are not expensive but i was told that you need to have a professional put them in it is something that you don't want to screw up that is the expensive part for me it was gonna be like 400 for front and rear gears and another 600 or so for the install i still want to do it but i am going to wait till it really need to then get nice big gears like 4.88 in the rear and 4.56 in the front.


    it is a good way of gaining power back you just have to have a pro put them in and that is the expensive part unless some one can install them that is in the club and if so give me thier number cause i wouldl love to see if they would give me a deal on a gear switch.

    bLaTaNt DiSrEgArD<br /><br /><br />TJ 98 4 banger gone but not fogotten<br />WJ 02 limited- Do all vehicle &quot;QUICK THROW A LOCKER AT IT!!!&quot;

    Quote from "omaha"

    gears like 4.88 in the rear and 4.56 in the front.


    you are kidding, right?


    Dr J,
    with a v6, 31's, and 3.73 gears you should be set up good. it should be quick. 4.10 gears would probibly be too low for 31's, but it depends on how your tranny is geared.

    Friday, UrbanCrawler and I took Quadna's Jeep to Dover Hardware to get some Grade 8 hardware for my strut install. His Jeep still seems quick and jumpy (I like that), but I wasn't driving. I miss that, but certainly want to keep the bigger tires, maybe even go to a little bigger next time. I thought maybe this was a solution...maybe not.

    you just gotta weigh your pro's and cons. gears will make it quicker from the start, but you will run at higher rpm's on the hiway.
    just more things to consider

    Argh, Argh, AAAARRRGGGGHHH!!!!


    I wanna go!



    I crawled under my Jeep in the parking lot, and didn't see any markings on the 8.25", where would they be specifically?

    Quote from "KJ04"

    Did you look on your axles to find out what it had for gears. KJ's come standard with a 4.10 and you can opt for 3.73's. I had the off raod group and a tow package on mine which they then put 3.73's in it. There should be a label on the axle tube or the diff cover.



    ...so if i have 4.10, would it be worthwhile to go to 3.73?

    From Jeep.com:


    4.10 Axle Ratio
    MSRP: Included
    A numerically lower axle ratio results in lower engine rpm and better fuel economy. A numerically higher ratio improves acceleration, climbing grades, carrying loads or pulling a trailer.



    So I guess I have 4.10. What happens if I switch? Sounds like I'd LOSE acceleration, since a lower numerical ratio would be 3.73:1. I'm not a math person, but doesn't a larger difference between the numbers mean a higher ratio?


    DrJ (art person)

    if that is not the setup i want then what should i be running if i want 32's on my 4 banger i have 4.10 now i don't know much about gears just the bigger the more power or atleast that is what i understand i could be way off if so some on egive me the heads up on what to do. I want the power back when i get the bigger tires. i have 31's now and i have lost power with them so i know it will be worst once i get a size bigger.

    bLaTaNt DiSrEgArD<br /><br /><br />TJ 98 4 banger gone but not fogotten<br />WJ 02 limited- Do all vehicle &quot;QUICK THROW A LOCKER AT IT!!!&quot;

    Quote from "turtle"

    http://www.rocky-road.com/kjdrive.html Looks like it would be straight forward as the 8.25" has plenty of gear choices and it looks like the IFS pumpkin takes standard dana 30 gears.



    I went to their site...THANKS! (I had a little problem with them on my lift kit, guess I'll have to get over it, they have some great stuff). I think I'm running stock 4.10 according to Jeep's website. Why would this site sell the 4.10 if the 3.73 is the preferred ratio for off-road? Are they assuming an off-road Jeep would have the 3.73 and is trying to get a little performance back? Their site says:


    "Feeling a loss of power with your oversized tires? Well, correcting axle gear ratio is a definite must to correct for performance losses caused by oversized tires. Notice how when you put those larger tires on, you lost both top end power on the highway and torque offroad. The key is keeping your engine in it's optimum RPM range for the best performance. Larger tires change the effective gearing on your vehcle, so new ring and pinion gears make sense for any tire from 31" on up to correct for this."


    Then they offer 4.10 and 4.56 gearing only...no 3.73.


    SO...it seems, reading all of this, that going to 3.73 might be better off-road, but would worsen my acceleration and passing, etc. Right? If so, you all are going LOWER for more grip and torque off-road, hence the 3.73, etc. If that is true, would 4.56 really suck off-road, but be quicker on (and give me better mpg)? For greens and blues only, I might consider 4.56 if I knew it wouldn't hurt us the 6-8 times a year we go off-road.



    ...whew!!!



    DrJ (thought 4.56:1 was the ratio of scotch to water)

    i think quadna is running 4.56 on his jeep not sure if that is right or not but i think that is what he said.

    bLaTaNt DiSrEgArD<br /><br /><br />TJ 98 4 banger gone but not fogotten<br />WJ 02 limited- Do all vehicle &quot;QUICK THROW A LOCKER AT IT!!!&quot;

    Quote from "omaha"

    i think quadna is running 4.56 on his jeep not sure if that is right or not but i think that is what he said.



    Ah Ha! That would explain the torquie-ness! Is that true Quadna?


    Would that snap off my axles when I floor it at a light? (overkill?)


    low numbers = better off-road (torque for crawlin')
    high numbers = better on road (acceleration/mpg)



    DrJ (maybe beginning to understand...maybe.)

    Chris has 4.88's in his TJ, running on 37" tires. That gear ratio brings his performance curve back into line with stock. I'm running 4.56 gears on 35" tires, which is also pretty close to stock.


    As you move to bigger tires, to keep performace at the same level you'd want to go to bigger gear ratios.


    If you're more concerned about highway cruising and fuel economy, then maybe a lower gear ratio would be better, but it will make low speed maneuvering (starting from the stoplight, crawling through mud and snow and over rocks) more difficult. Higher gears will give you better low speed control, but your engine will rev higher at your normal highway speed and burn more fuel.


    Of course, I think you have an automatic transmission, and that changes the way that all the parts play together. I don't think there is any reason for you to change gearing until you get your solid front axle and 35" Krawlers.

    Former Trail Boss (2003 - 2005)

    Edited once, last by ().

    but then why should we regear for bigger tires if it is better to have low gears off road and we are putting higher ones in? if i go to bigger ones will i suck off road?

    bLaTaNt DiSrEgArD<br /><br /><br />TJ 98 4 banger gone but not fogotten<br />WJ 02 limited- Do all vehicle &quot;QUICK THROW A LOCKER AT IT!!!&quot;

    If you have 4.10 gears stock, you would be going backwards in getting 3.73's. The numbers get higher but the gear ratio's are actually lower.


    If you having "power" concerns, then you want higher numerically gears, ie 4.56 or above. Although, I wouldn't think that you would even want to run 4.56 with only 31" tires.


    My stock ratio's were 3.73 with my stock 30" tires. I have since regeared
    to 4.56 with my 35" tires. My RPM's are pretty close to stock on the highway - around 2100-2200 at 60-65mph. Offroad, I'd like even lower gears (4.88's) but that would make my highway RPM's even higher.


    Clear as mud? For you, cost wise and RPM wise I'd stick with your stock gears if they are 4.10's. Even if they were 3.73's, the cost probably wouldn't justify the jump only to 4.10's.



    Joe


    Edit: Andrew beat me to it!!!

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