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re-gearing question

1498 Views 12 Replies 10 Participants Last post by  foxinthemudd
ok, i have done my reading and research and have decided to re-gear my 99 tj 2.5L. i am going to put 31 inch tires and i don't want to loose power. what i need to know is what gear ratio i should get? and what rear axle do i have on my stick jeep? and where i should go to but it?
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i dont think with 31 inch tires u would feel a power loss. But if u were to spend the money and regear, i would do atleast 4.56, because u would problaly go larger later on.
i would like to gain some power as well if possible, i was told that cold air filters, exhaust, chip, etc are all a waist of money and go just spend it on re-gearing.
regearing is a great way to make up for lost power but your only running 31's. with 31" tires 4.56 is ideal with your 4 banger and thats not a huge jump from may can feel a difference though
You have the 4 cyl go with the 4.88s they will work and if you ever go to 33s you are ready.Also now is the time to do lockers or limited slips.Bill
Now is a realgood time to figure out how big tires you are going to end up with. You are not gonna be happy if you spend 2k now, than 4 months from now go to 33s or 35s and need to re-gear again. I think for 31s its useless unless you re gear high enough to compensate for taller tires later... but thats just one mans opinion.

Also, if you offroad or plan on starting, choose some lockers now unless you never plan on locking. Another waste of $ to crack open the diffs again 3 months from now
It's not worth the $1200 (give or take $100) to only regear from your present 4.10 to 4.56, there's simply not enough difference betweeen those two ratios. And for only 31" tires, don't bother as you haven't lost that much performance yet. When you get to 33", it'd be appropriate to regear to 4.88 which is a real nice all-around combination for your 4-banger. :)
If you are going to 31's, keep the 4.10's. I ran 30's on mine for a few years.

Save the $$ for when you want to go to 33's, Super 35 and locker and go to 4.88.

4.56 is a good ratio for 32's.

My 97 TJ 2.5L is running 4.88 and 33x12.5's. I upgraded the D35 to a Yukon 35 with ARB and 30 spline shafts and put in a lockrite at the same time.
ok, so now how do i get some extra power? i had posted a thread about intakes and exhausts and gaining power and was told by several to re-gear. now i shouldn't bother if i am not going to go up to a 33" tire? what would be that most cost effective way to go?
re-gearing to the right ratio will do 100% more than any "power-mod" for your jeep, other than a V8 swap... if anything go one gear size higher to benifit the most.
now i shouldn't bother if i am not going to go up to a 33" tire? what would be that most cost effective way to go?
Exactly, wait until you get to 33" tires to regear. Power-wise, there's nothing cost effective that will make a worthwhile difference on your 2.5L... short of a turbocharger or supercharger. All the other stuff like headers, cat-back, etc. are darned expensive for the extremely minor improvement they sometimes make. :)
Avenger Superchargers.....full exhaust and a good tune
I run 31's on my '98 and just installed a header and had a flowmaster catback, with a tune up on my 2.5. and noticed a difference, however slight, but a difference. and it sounds much better (if your into that). I think that I am going to do the air intake later for sound and cooling, but the next thing is a new RAD. due to the S*$&&$ planning on mopar with the plastic/metal combo.
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