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Old 02-23-2012, 04:10 PM   #1
Join Date: Jul 2006
Location: columbus
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gear / axle upgrade ?'s

hey guys. heres the issue. my 91' - 4.0L - 5spd, is factory with 3.07 gears. im currently on 31's and it pretty much lacks any bottom end power (this is with a freshly rebuilt engine) i'm looking to upgrade my gears OR axles. I know that the D35 is notoriously weak. and i'm ocd about if you're going to do something, you might as well do it right. I dont plan on larger tires anytime soon as its my DD, but down the road i'll probably go up to 35"s MAYBE 37". I dont do alot of hard wheeling, just around the hunting land in central GA. alot more mud / red clay than anything.

I've heard that the d35 i have will only accept up to 3.73 gears? i dont think that will low enough once i eventually get larger tires. So what i'm thinking is just replacing the rear axle with a completely different axle. would a YJ D44 be fine? and what gears could that go up to? its not all about price but its also not that money is no concern, i'm looking for best quality for the best price that will get the job done with no problems.

is the D30 up front a strong enough axle for my use? or should i get something better. i was thinking just match the gears in it to whatever i put in the rear and run chromoly shafts.

undecided on if i'll go SOA or remain SUA on when i do finally go to larger tires. will probably just depend on my money situation at the time.

so, what advice / info etc? this is nothing i'm doing right away, probably within the next year, just wanting to get info together so i can plan exaclty what all i need to buy so that i can price it out and start collecting materials for the build.

also, for now, what gears ( that will fit in my diff) would be better for my 31's? i've basically got highway gears now. i dont need super low granny gears that max my top end out at 55, but would like a little more power in the bottom end

Thanks guys

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Old 02-23-2012, 04:57 PM   #2
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37's, no and no. 35's on a D30 from chromo shafts and no lead foot.

The deepest gears you can get to match with a D35/D30 combo is 4.88. The 3.73 information you got is where the carrier break is (where you need a new carrier). With your 3.07 gears you'll need a new carrier front and rear. Your *ideal* gear ratio with 31's is actually 3.54/3.55 gears, but that's kind of a pointless upgrade if you're planning on running bigger tires in the future.

There is no YJ D44, at least not stateside. Easiest swap for the rear is a XJ Dana 44, but good luck finding one. They're rare. Next easiest is a Ford Explorer 8.8.

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Old 02-23-2012, 05:31 PM   #3
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thanks bud, thats the exact kind of info i was looking for. what kind of alteration would have to be done on the xj 44 or the 8.8 other than putting the spring perches in the right spot?

also, since the d30 up front would be at its limit, what would be the next axle to step up to that would do the job?
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