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Unread 02-12-2013, 10:43 PM   #1
Exit93
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1991 YJ Wrangler 
 
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differential question!

So here the situation. The P.O. Of my 91 wrangler somehow tore up the rear diff, got it fixed but with the wrong gears(I'm not sure with what ratio) The front is stock, I'm not sure what it is though. The problem is that the front doesn't match up with the back so 4 wheel drive is a big no go. My question is what should I do? Get the front regeared to match the back since they are stock and are 22 years old? Get the back regeared to match the front? Or get them both regeared to something new? This is mostly street and some high way driven, and in the near future I would like to get it dirty. I'm driving on 31's too, if that makes any difference

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Unread 02-12-2013, 10:55 PM   #2
Joe Dillard
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How do you know for 100% sure if they are different ratio's?
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Unread 02-12-2013, 11:08 PM   #3
Anticanman
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What ratios are they?
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Unread 02-13-2013, 06:35 AM   #4
troy.j
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re-gear with future tire size in mind. if you want to save some cash re-gear to the one that is the nearest to the ratio you want.

you will need to figure out what ratio you have first. look at FAQ section.
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Unread 02-13-2013, 07:59 AM   #5
Exit93
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Quote:
Originally Posted by Joe Dillard View Post
How do you know for 100% sure if they are different ratio's?
if I put it in 4 wheel drive, the front wheels spin at a different speed then the back
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Unread 02-13-2013, 08:00 AM   #6
Exit93
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Quote:
Originally Posted by troy.j View Post
re-gear with future tire size in mind. if you want to save some cash re-gear to the one that is the nearest to the ratio you want.

you will need to figure out what ratio you have first. look at FAQ section.
I plan on keeping the 31s, what's the ideal ratio for them?
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Unread 02-13-2013, 08:10 AM   #7
pete1991YJ
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Mine is on 31's with 4.10's but it would be ideal on 4.56's. This is with the factory 4-banger.
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Unread 02-13-2013, 09:21 AM   #8
Joe Dillard
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Quote:
Originally Posted by Exit93 View Post
So here the situation. The P.O. Of my 91 wrangler somehow tore up the rear diff, got it fixed but with the wrong gears(I'm not sure with what ratio) The front is stock, I'm not sure what it is though. The problem is that the front doesn't match up with the back so 4 wheel drive is a big no go. My question is what should I do? Get the front regeared to match the back since they are stock and are 22 years old? Get the back regeared to match the front? Or get them both regeared to something new? This is mostly street and some high way driven, and in the near future I would like to get it dirty. I'm driving on 31's too, if that makes any difference
Other than brake pads, personally, I would not put a dime into the rear D35 axle.

I would also not regear the front simply due to age. Here's why......although the gears are ~22 years old, there is probably super low wear on them due to the only time they see wear is when its in 4wd.

In other words, you may have 10,000x's less wear on the front gears than the rear has even if the old rear gears were still installed. Make sense?

Quote:
Originally Posted by Exit93 View Post
if I put it in 4 wheel drive, the front wheels spin at a different speed then the back
I would junk/sell the rear axle & swap in a different axle (EG: D44, Ford Explorer 8.8 etc) with the gears to match the front.
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Unread 02-13-2013, 09:35 AM   #9
troy.j
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on 31's with the 4.0 i wouldn't gear deeper then 410. my wife's yj is soa on 33's and runs great on the 3.73's in it, but 5th is useless till we hit 70 or so. mpg on the freeway in 5th for 2500 miles was in the high 20's for most the trip pulling a trailer. dropped to under 20 pulling the Rockies in 4th most of the way. acceleration? still blows my 99TJ 2.5 away on the 31's with 4.56 gears. both jeeps are 5spees stick.
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Unread 02-13-2013, 10:33 AM   #10
Exit93
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Quote:
Originally Posted by Joe Dillard View Post
I would junk/sell the rear axle & swap in a different axle (EG: D44, Ford Explorer 8.8 etc) with the gears to match the front.
so your saying to swap the back? how hard is it to swap axles? it would be a first for me. and the big question is how much will it cost me?
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Unread 02-13-2013, 11:06 AM   #11
troy.j
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Quote:
Originally Posted by Exit93 View Post
so your saying to swap the back? how hard is it to swap axles? it would be a first for me. and the big question is how much will it cost me?
The dana 35 has a bad rap, and rightly so, jeepers like to lift their jeeps, stuff larger tires, add lockers, boost horse power and modify suspension components then drive them where god only intended deer to travel.
YES, I AM IN THAT GROUP.
But the 35 is plenty strong for 31’s and even up to 33’s as long as you don’t drive like a fool.

You plan to stay on 31’s and daily drive it with light wheeling… I wouldn’t change the rear-end. Its not worth the money, just re-gear. I know some will say it can be cheaper to swap, and that CAN BE true if you have the tools and the knowhow.

No offence, but it doesn’t sound like you have ether. Your jeep will live a long happy life with a 35 in the rear.


ps, your jeep came with the 35 in the rear. if the PO swapped in a 4 banger 35 rear you now have 4.10's

do you know if the PO swapped rears or had the original fixed? not many jeepers would swap a 35 for another 35 unless they were flat broke and someone paid them to do it, you may have a better rear all ready.

if he fixed it himself i would worry about him slapping in a used carrier and gears for a quick sell without proper setup. just a thought.
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Unread 02-13-2013, 11:19 AM   #12
troy.j
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figure out for sure what axles and ratios are in your jeep, then post back.
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Unread 02-13-2013, 11:29 AM   #13
Exit93
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I'll climb under it today, I know for sure the back was regeared and not swapped with another 35
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Unread 02-13-2013, 04:49 PM   #14
Mark05059
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take pictures of the rear so we can id it
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