Tire size and gear ratios - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-12-2000, 07:51 PM Thread Starter
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Tire size and gear ratios

Right now I'm running a fresh 304 with no specific performance modifications
mated to a TF-999 automatic and D-300. My gearset is 3.31 with BFG-33's
What little investigation I've done seems to say that I should be running
about a 3.73 gear set for good all around performance. As it stands I'm
fairly happy with the giddyup on the road and am getting decent mileage.

I'm on the verge of doing some axle work, whether it be 1 piece rears in the
model 20 or swapping in a 44, and adding lockers of some sort. Now would be
the time to do a gear change.

I intend in the future to move up to some 35's and herein lies the dilema.
I'm pretty happy with performance as is with 3.31's when the "book" says I
should be somewhere around 3.73. Since I'm happy where I am performance
wise could I bump up to 3.73's with 35's and expect the same general
performance as I have now?

Since I live in Ohio and rockcrawling is not much of an issue around here I
am not looking for gobs and gobs of crawl ratio. Mild to moderate
trail/muddin will be about the extent of it with "this" rig. I would much
rather have some decent "all around" performance, leaning towards on road
giddyup/fuel economy, and if need be get some off road grunt via a lowered
gear set for the D-300. Am I on the right track here considering my
specific usage or am I way out in left field?



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post #2 of (permalink) Old 12-12-2000, 08:27 PM
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Re: Tire size and gear ratios

[img]/wwwthreads_images/icons/smile.gif[/img] Dear spooked in Ohio. If the performance of your Jeep is at a level that you deem satisfactory, you can preserve that level of performance if you just maintain the same number of engine revs at 60 MPH when you make the changes. Find the number of turns per mile that the tires have NOW. Multiply that by the rear end ratio you have now, and that gives you turns-of-the-driveline-at-60-MPH. If you divide THAT number by the new turns per mile of the bigger tires, the calculator will spit out the new rear end ratio that you will need. So: Turns/Mile(old)X Ratio(old)=Turns/Mile(new)X Ratio(new) You can easily get the turns per mile of the tires from the dealer catalogs. I can send a moonguy crew to Ohio to assist you, but these guys can get expensive when you consider airfare, hotel, booze, broads, and bread.[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
Quadra-Tracs modified While-U-Wait by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img] Quadra-Trac Team.[img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
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post #3 of (permalink) Old 12-13-2000, 12:35 AM
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Re: Tire size and gear ratios

hey spook where u located at in ohio? i'm around cleveland..

(\/)ikey
1988 Wrangler Laredo 4.2L w/5spd Manual
1995 Wrangler 2.5L w/ 5spd / 31"BFG AT's
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post #4 of (permalink) Old 12-13-2000, 06:39 AM Thread Starter
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Re: Tire size and gear ratios

Wrangler: I'm in Canton. About 60mi south of Cleveland. Land of Cleves.

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post #5 of (permalink) Old 12-14-2000, 07:10 AM
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Re: Tire size and gear ratios

Cleveland, the mistake on the lake?.....Has the river caught fire lately? Sorry. I'm originally from Pittsburgh. Actually I heard that they're pulling walleye from that river now.

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post #6 of (permalink) Old 12-14-2000, 09:53 AM
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Re: Tire size and gear ratios

CJDave--"Booze, broads, and bread."???? Those moonguys have THE LIFE!!! They must be in college... hehehhe

mike

Give me Jeep or Give me Death!!!

(Will trade functioning organs for CJ-7 or flatfender)
post #7 of (permalink) Old 12-14-2000, 12:31 PM
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Re: Tire size and gear ratios

[img]/wwwthreads_images/icons/smile.gif[/img] It's hard to beat a good moonguy[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img]crew, be it workin' or just plain livin' it up![img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
Quadra-Tracs modified While-U-Wait by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img] Quadra-Trac Team.[img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
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