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Old 07-11-2013, 12:49 AM   #1
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Re-gearing my 2.5l question!!

picture the scene. i am running 31" tires on my 2.5l 4 banger and i live in a place that is covered with hills. i have been looking into re-gearing to 4.56 to try and get my 5th gear back.

i am a little tight on money and don't want to buy the cheapest gears out there. i am trying to save some money on the install and since i would never trust myself with this i was wondering if it was possible to only re-gear the rear axle.

i rarely go off-roading due to school, work, and no close-by trails........i know its a shame

i am new to the automotive world and this is my first vehicle so please don't be offended or too harsh with your replys
thank you

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Old 07-11-2013, 12:57 AM   #2
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No you must regear both axles. If you don't then your rear wheels will be spinning at a different speed then your front wheels.

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Old 07-11-2013, 01:19 AM   #3
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Yeah...as above, regear both axles...going to run you around 1200 give or take
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Old 07-11-2013, 02:01 AM   #4
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You can regear only one axle at a time. However, you have to remove one of the driveshafts (front if you only regear the rear) so you can't use 4wd.
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Old 07-11-2013, 07:37 AM   #5
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Really? I thought the answer that I was going to see to his question was that he could just do the rear, but he couldn't put it in 4wd. Shows how much I know I guess. Why does the front driveshaft have to come out if he keeps it in 2wd?
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Old 07-11-2013, 08:11 AM   #6
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Really? I thought the answer that I was going to see to his question was that he could just do the rear, but he couldn't put it in 4wd. Shows how much I know I guess. Why does the front driveshaft have to come out if he keeps it in 2wd?
To avoid binding in the t-case
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Old 07-11-2013, 08:16 AM   #7
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No, the front driveshaft does not need to be removed if the f/r axle ratios do not match. Absolutely not required. You couldn't use 4x4 but that's it.

And not even factory front/rear axle ratios match precisely... with the exception of the Rubicon with matching f/r axles, Jeep axle ratios are generally .01 different between the f/r. As in 4.10/4.11, 3.73/3.74, 3.54/3.55, 3.07/3.08. And even if they match precisely as the Rubicon's do, the front & rear axles still turn at different rpms since the front tires rotate faster than the rears do on turns or curves.
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Old 07-11-2013, 08:18 AM   #8
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To avoid binding in the t-case
So even in 2wd you're still "connected" to the rear axle?
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Old 07-11-2013, 08:21 AM   #9
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So even in 2wd you're still "connected" to the rear axle?
Nope, at least not if I understand your question. The sporadic advice that you somehow "must" remove your front driveshaft if your axle ratios don't match is not true for a Wrangler TJ. You just need to avoid using 4x4.
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Old 07-11-2013, 08:36 AM   #10
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As Jerry said you do not absolutely need to disconnect the front driveshaft. When the transfer case is in 2wd both the mainshaft and the front output shaft can both move independantly as the T-case drive chain is not linking them in unison.
But removing the front driveshaft can keep you from accidentally engaging 4wd and causing yourself a world of headaches.
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Old 07-11-2013, 08:41 AM   #11
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But removing the front driveshaft can keep you from accidentally engaging 4wd and causing yourself a world of headaches.
I dunno about you but I have never accidentally engaged 4x4. And if you're sitting still & engage 4x4, the most that will happen is things will start binding as you start to drive off... but it will bind up enough to stop you at a still slow speed, not break things. You'd have to try real hard like engaging 4x4 at highway speeds with good traction... you know, stupid stuff... before any damage might occur. Keep in mind that not even the factory f/r ratios are perfectly matched... and even if they were, you still can't drive in 4x4 on a high traction surface or highway without it eventually binding... it would still bind up for the reason mentioned in my earlier post.
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Old 07-11-2013, 08:56 AM   #12
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I dunno about you but I have never accidentally engaged 4x4. And if you're sitting still & engage 4x4, the most that will happen is things will start binding as you start to drive off... but it will bind up enough to stop you at a still slow speed, not break things. You'd have to try real hard like engaging 4x4 at highway speeds with good traction... you know, stupid stuff... before any damage might occur. Keep in mind that not even the factory f/r ratios are perfectly matched.
I would agree with you. I have never accidentally engaged my 4wd and dont see that happening. I was more thinking on the lines of stupid stuff like you said. Someone forgetting and engaging 4wd in low/no traction situation and then carrying some speed on to solid ground. I dont know how much force it would take to start breaking stuff, but i do know people do stupid things and somehow find a way for people to say WTF.

If it was me I wouldnt remove my front driveshaft, but just wanted to point out that it is still an option.
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Old 07-11-2013, 10:52 AM   #13
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Originally Posted by Jerry Bransford View Post
Nope, at least not if I understand your question. The sporadic advice that you somehow "must" remove your front driveshaft if your axle ratios don't match is not true for a Wrangler TJ. You just need to avoid using 4x4.
Thanks for the clarification, Jerry. When I posted that question your First post hadn't showed up for me yet. That's how I always understood it, that you were in no way connected to the front in 2wd. Just thought I might have been missing something, as I know there are a lot of folks on here that know more than I do.
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Old 07-11-2013, 10:53 AM   #14
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Sorry it was early and as I was cutting my grass I realized that what I said wasn't true and I was just getting back on to say that. But thanks for the correction Jerry!

However, if you're worried about someone else accidentally engaging it (I don't typically let other people drive my Jeep, very few have, but some people are more giving than me ) or if you're real forgetful, it still might be a good idea in my opinion
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Old 07-12-2013, 06:39 PM   #15
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thank you guys so much for all of the replays.

so what i am getting from all this is that it is possible but once it is done i can't use 4hi/4low. its kinda what i guessed.

it will only be temporary until i can make enough money to re-gear the front axle.

is there anything else that i need to worry about?
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Old 07-12-2013, 06:49 PM   #16
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Nope.
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Old 07-14-2013, 12:28 PM   #17
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one last question. exactly what do i need to buy for this project. ring? pinion? gear?

also what is a good website to order off of?

and finally what is a good brand?

sorry for all of the questions.

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Old 07-14-2013, 01:01 PM   #18
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I just regeared my 4 banger. It's a manual which had the 4.10s. I am running a 285 series tire(about a 32-33) and the 4.88s are not all that overgeared. What I'm saying is I would not go to the trouble of regearing unless I was going all the way to the 4.88s. If yours is a auto, it may be different. I've heard they pull better with the lower(numerical) numbers. I now can use 5th gear all the time, whereas before it was only on the interstate while running downhill.
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Old 07-18-2013, 05:24 PM   #19
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mine is manual. i hear that if i were to regear it to 4.88 then i will loose my top speed but will gain acceleration i am just looking for something in-between because i don't think that i will run any tires bigger than the 31s i got on it
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Old 07-18-2013, 05:52 PM   #20
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mine is manual. i hear that if i were to regear it to 4.88 then i will loose my top speed but will gain acceleration i am just looking for something in-between because i don't think that i will run any tires bigger than the 31s i got on it
4.88 gearing for 31" tires would be excessive for sure. However, 4.88 gears would however be very appropriate for the 2.5L engine and 33" tires and would actually restore top speed lost with the factory 4.10 gearing after installing 33" tires. For your 31" tires, I wouldn't change your existing 4.10 gear ratio.
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Old 07-19-2013, 08:24 PM   #21
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4.88 gearing for 31" tires would be excessive for sure. However, 4.88 gears would however be very appropriate for the 2.5L engine and 33" tires and would actually restore top speed lost with the factory 4.10 gearing after installing 33" tires. For your 31" tires, I wouldn't change your existing 4.10 gear ratio.
i really want to do something that will allow me to get around town without the need to down shift to 3rd every time i hit a hill. there are no flat streets in my city. its all hills

do you think that 4.56 gears would help
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Old 07-20-2013, 12:54 AM   #22
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I am running 31s with 4.56 gears , it makes a big difference in the drivability of my Jeep both on and off road. If you can afford it I say go ahead and regear.
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Old 05-09-2014, 10:07 PM   #23
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well i havent regeared and actually went ahead to get 33s. i got the 33x10.5 just to make it a bit easier on the engine. now i really do need to regear. will regearing to 4.88 help or make my mpg go down
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Old 05-10-2014, 03:25 AM   #24
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I live in a "hilly" area and 4.88 with 33's will kinda feel like 31s with the 4.11 ratio, just a hair better IMO. I have a 2.5 with 4.88s and 35s, not the best feeling but do able... just put on my old 31s for a "safety check" and it feels good driving around town but I always had a thing for burnt rubber...
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Old 05-10-2014, 09:52 AM   #25
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you have to remove one of the driveshafts
Did you read any of the replies in this thread?
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Old 05-10-2014, 09:59 AM   #26
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Did you read any of the replies in this thread?
just an fyi that post you questioned was from a spammer.. they are gone now..

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