Looking to adjust my gear ratio

I've found it extremely helpful in the past to get advice from this board before I go ahead and dish out my hard earned cash. My question pertains to gear ratios. I've heard over and over that you lose alot of acceleration off of the line when you increase your tire size. I've checked out some websites that supposedely have formulas that tell you what you should change your gear ratio to, but I'd rather hear from someone directly.

I have a 3" rancho RS5000 lift on my 2000 XJ. I've had 31x10.5x15" Goodyear Wrangler AT/D's for about two years now. My Jeep originally came with 225x75x15" Goodyear RT/S's. What gear ratio would restore everything back to factory? Or, would I be better off going for a ratio lower or higher than factory? Is it expensive to have your gear ratio changed?

Any advice would be greatly appreciated!

regearing is always a good idea, but you want to anticipate for the possibility of going with larger tires in the future. somewhere between 3.73 and 4.10 would put you back to stock technically, but with the added weight and drag of a lift and bigger tires, it will feel much better with 4.10s. If there's ANY possibility of going to 33s in the future, just get 4.56 gears now.

the cheapest way would be to find some stock axles that came with 4.10s (i'm assuming you have a 4.0L, auto tranny which comes with 3.55 gears), that could be as little and $200 or even free if you have the right friends. to get the axles professionaly regeared with new gears would cost probably over $1000, depending on where you live, and you might as well add lockers while you're at it.

do you eventually want to go bigger? if you're fine with your tire size, then go with 4.10. i actually have 4.56's with 31's but thats only cause i'll be going to 33's within the next week... is your XJ an auto or 5 speed? gear changes are kinda expensive, so plan to do it right the first time! i'd say about 200-300 per axle. pm rawbrown, he can hook you up with some good gears!

but in the mean time, DO A SEARCH!

hope that helps
brandon

Wow, I did not anticipate that new gears with all the trimmings would cost over 1000$. Unfortunately, I no longer live in Flagstaff, AZ, so there isn't the over abundance of offroad specialty shops in Boston, MA as I was used to. Plus, EVERYTHING in Boston is more expensive. Would I be better off trying a junk yard for the axles with the 4.56 gears?

BuddhaBudz said:

Wow, I did not anticipate that new gears with all the trimmings would cost over 1000$. Unfortunately, I no longer live in Flagstaff, AZ, so there isn't the over abundance of offroad specialty shops in Boston, MA as I was used to. Plus, EVERYTHING in Boston is more expensive. Would I be better off trying a junk yard for the axles with the 4.56 gears?

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you could look, but i would get new ones. this is just becuase of the unknown wear on the used ones you would find. plus 4.10's would be easier to find maybe in a 8.8 axle but harder in a Dana... what axles do you have? this could cut down on the cost.

As mentioned, try searching for a ford 8.8 out of an Explorer with 4.10 ratio for the rear. It might have a Limited Slip Diff as well.

For your front a TJ LP D30 w/ a 4cyl would be a good cheap swap for the front. This is just like yours in your 2000.

Even better would be any XJ w/ a 4 cylinder, with in the years of 91-98. They also have 4.10 and are High Pinion D30 front axle.

try searching www.car-parts.com , check Boston and the surounding area.

Are you amember of any offroad club or have friends with gear install experience?

I was hopelessly going to have to pay $1k (price around here) for just labor. Then I asked around and had a guy in my club with a buggy on 49s offer to help install for free. I haven't done it yet, but free is always best for me.

In terms of engine RPM to road speed, 31x10.50R15 tires with 3.73 gears is exactly the same as stock tires with 3.54 gears. If you really want to get back to stock, go with 3.73s.

However, pay attention to those who are recommending more gear. Those 31s are a lot heavier than stock tires, so you automatically need more "ooomph" to get them rolling. Plus the almost inevitable urge to move up to still larger tires. Regearing isn't cheap ... it would be a shame to do it and soon thereafter decide you didn't go far enough.

I'm happy with 31s and 3.73 gears, but most people would not be. And in all honesty, I chose the gears to run with 30" tires, and went to 31s only because my brother gave me his old set.

i'm runnin to a junkyard about an hour from boston tomorrow.

I know there's a '95 or 96 4-cyl cherokee in the yard there

prolly has 4.10s

I'll look at it and see if they're still there, what gears they are and ask 'em what it'll cost to get them. (if i remember)

you'll hafta pull 'em yourself.

what rear axle do you have?

BuddhaBudz said:

Wow, I did not anticipate that new gears with all the trimmings would cost over 1000$. Unfortunately, I no longer live in Flagstaff, AZ, so there isn't the over abundance of offroad specialty shops in Boston, MA as I was used to. Plus, EVERYTHING in Boston is more expensive. Would I be better off trying a junk yard for the axles with the 4.56 gears?

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If you're willing to travel into Rhode Island, try Victory Auto in Burrilville, RI. It's north of Providence by about 20 minutes.

You won't find 4.56 gears in a junkyard XJ -- that wasn't a factory ratio. You may find 4.10s in a 4-cylinder.

I ran 3.73s when i first went to 31's and as Eagle points out, this gives you stock-like gearing. But as inchitis crept in and i went up more, I eventually went to 4.10s. The 4.10s again gave me stock like feel with 33s, but then again mine is mostly a daily driver and only gets wheeled on weekends...
Buck