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Old 04-18-2010, 01:32 PM   #1
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Gear ratio questions

Hey Guys,
Well the rear differential in my jeep decided to shit the bed on me the other day and it looks like we are gona throw some new new gears in it. I talked to a friend who has a good knowledge of mechanics and he says I should go with 3.50 or a 3.55 gear ratio. The jeep is a 97 with a 4.0 and 5 speed Hurst shifter. Ive got 33's on a 15 inch rim and was wondering if you guys could help me pick out the proper set of gears for this set up.

Thanks for the Help,
Matt

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Old 04-18-2010, 01:35 PM   #2
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Umm no- go with 4.56's or 4.88's. Your jeep will be all kind of pissed off at you driving on those gears. I run 5.13's in my jeep FYI on 33's.

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Isn't the JK just a rebodied PT Cruiser?!

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Just a few more inches Red. You can take it.


If you haven't gotten more out of the insurance company than you deserve, then you haven't screwed them nearly as much as they have been screwing you for the past xx years.
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Old 04-18-2010, 01:42 PM   #3
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Ok, how is the gas millage going to be like with those? My jeep is my daily driver and it only goes off roading occasionally. I just need something that is going to be reliable but still has potential for light off roading.
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Old 04-18-2010, 02:04 PM   #4
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Reminder - both axles must match
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Old 04-18-2010, 02:15 PM   #5
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Your driving a brick. Your gas mileage will be around 14 depending on how you drive-- IE lead foot etc etc
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Isn't the JK just a rebodied PT Cruiser?!

Quote:
Originally Posted by coyote_94yj
Just a few more inches Red. You can take it.


If you haven't gotten more out of the insurance company than you deserve, then you haven't screwed them nearly as much as they have been screwing you for the past xx years.
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Old 04-18-2010, 04:00 PM   #6
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I ran 4.56's on 33's for a few years. I would not recommend going any numerically higher with your ratio than that. 4.10's would probably be perfect, but if there is even a chance of bumping up to 35's later then 4.56 is a good choice.
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Old 04-18-2010, 04:13 PM   #7
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From what I have read on this forum...4.56 is ideal for 33's and 4.88 is ideal for 35s. That will regain any lost power, torque, performance or gas mileage.

And as Atthehop stated if you regear the rear differential you MUST also regear the front to match.
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Old 04-18-2010, 04:34 PM   #8
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Quote:
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I talked to a friend who has a good knowledge of mechanics and he says I should go with 3.50 or a 3.55 gear ratio.
Maybe he knows mechanics.... but not Jeeps or what axle ratios work with what tire size.
I'm running 3.73's w/32's and could stand to gear lower (higher number)
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Old 04-18-2010, 05:15 PM   #9
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BTW you say you have a 1997 4.0...chances are you already have 3.55 gearing. 97 was the only year that was offered and I think most 97 Wrangler "sports" came with that gearing. Check the tag on the diff cover and see what it says...there will be 3 numbers
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Old 04-18-2010, 06:02 PM   #10
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I don't know about most 97 Sports, but mine came factory with 3.07's. I put 33's on it in 2002 and it was a dog. I swapped in a Dana 44 w/ 3.73's and it was much better. I later regeared to 4.56 and it was just a tad too much gearing. I am now on 35's and the 4.56 gears seem to be the best fit for power and fuel economy-much better than it was on 33's with the same gears.
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Old 04-18-2010, 06:45 PM   #11
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Your right Ken...there was 2 options...3.07 or 3.55
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Old 04-19-2010, 12:29 AM   #12
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I have no idea why they ever made 3.07s. Those gears were horrible even with stock tire sizes.
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Old 04-19-2010, 12:41 AM   #13
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I had a buddy that has a 97 mustang v-6 that came from the factory with 2.73's hahahahaa
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Quote:
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Isn't the JK just a rebodied PT Cruiser?!

Quote:
Originally Posted by coyote_94yj
Just a few more inches Red. You can take it.


If you haven't gotten more out of the insurance company than you deserve, then you haven't screwed them nearly as much as they have been screwing you for the past xx years.
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Old 04-19-2010, 07:16 AM   #14
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I have no idea why they ever made 3.07s. Those gears were horrible even with stock tire sizes.
...to meet federal fuel economy requirements.
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Old 04-19-2010, 07:21 AM   #15
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4:10 is ok for those tires if most of your driving is on the flats. Else 4:56 to make it feel like a Jeep.

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