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post #1 of 9 Old 04-06-2007, 11:39 PM Thread Starter
red92YJ
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Question on gearing

I put a new set of 31x10.5 M/T tires on my Jeep a few months ago to replace the 31x10.5 A/T's that were on it. The new tires are an inch or two taller than the old tires I guess the height difference is because I went to an M/T tire and I noticed a significant power loss at highway speed (65-70 mph). Low end power is still pretty good but it is a dog in 5th gear. My gas mileage has also dropped way off. I can live with poor gas mileage but would like more top end power.

From what I can see on the tag on the rear end said 3.07 gears in the rear end. I believe it is all stock. I don't do any serious off roading other than running around the woods during hunting season so it is used mostly on pavement.

I was wondering what gear ratio would be good for top end power increase. I was thinking 4.11 or 4.27 but then again I know next to nothing about what would be best? What say you experts out there?
The Jeep has the 4.0L 6 cyl with 5 speed manual transmission.

Thanks in advance for any advice.


1992 red YJ soft top 4.0 w/5 speed BF Goodrich 31x10.50 M/T tires, 1.25" shackle lift, Rancho RSX shocks, Outland Neoprene seat covers, Outland Acoustic brief bikini top, KC lights (windshield and bumper)
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post #2 of 9 Old 04-06-2007, 11:41 PM
mean90yj
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i run 3.73 in my jeep, i have 32" bfg m/t's, fifth gear is no problem at all, kinda sucks on a windy day goin down the road but then again its a brick with wheels. i have a buddy who has 4.10's but thats cuz it came stock with his 8.8. Something in that range will do you just fine for going in the woods hunting and keeping it drivable on the highway.

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post #3 of 9 Old 04-07-2007, 10:15 AM
RockWoRM
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Quote:
Originally Posted by red92YJ
I was wondering what gear ratio would be good for top end power increase. I was thinking 4.11
.
I would go the 4:10/4:11 route if your gona run 32's. That should get ya your 5th back.
U have a couple options... pay to re-gear or shop arround for a good set of axles from a 4 banger w/5sp. Those would be fac. 4:11's.
Re-gear costs could run ya any where from $1000.oo - $1200.oo for the pair... give or take, depending on who, what, where.



WoRM

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post #4 of 9 Old 04-07-2007, 11:37 AM
Joe Dillard
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Quote:
Originally Posted by red92YJ
I was wondering what gear ratio would be good for top end power increase.
Have you tried playing around with one of these yet to see what numbers you'll be looking at?
http://www.manoian.net/jeep/gear_ratio_calculator.html
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post #5 of 9 Old 04-07-2007, 12:18 PM Thread Starter
red92YJ
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Quote:
Originally Posted by Joe Dillard
Have you tried playing around with one of these yet to see what numbers you'll be looking at?
http://www.manoian.net/jeep/gear_ratio_calculator.html
I looked at the chart on the 4wd.com catalog I just got and it was showing 4.11 was middle of the road for my tire size and what I use my Jeep for. They have a special going on gear sets (front and rear) with the master install kits included for $399. Is this a good thing?
Next dumb question...
Do I need to do the front and rear with the same gearing or can I just do the back?


Quote:
RockWoRM
I would go the 4:10/4:11 route if your gona run 32's. That should get ya your 5th back.
U have a couple options... pay to re-gear or shop arround for a good set of axles from a 4 banger w/5sp. Those would be fac. 4:11's.
Re-gear costs could run ya any where from $1000.oo - $1200.oo for the pair... give or take, depending on who, what, where.
That seems kind of high. If I can get the parts for $399 then I would think labor would only be about the same as the parts cost. Am I wrong?
I'll still get it done because I want the top end power but I was hoping to get out for about $800.

1992 red YJ soft top 4.0 w/5 speed BF Goodrich 31x10.50 M/T tires, 1.25" shackle lift, Rancho RSX shocks, Outland Neoprene seat covers, Outland Acoustic brief bikini top, KC lights (windshield and bumper)
Sound bar and JVC HD radio.
http://img.photobucket.com/albums/v3...g?t=1176762892
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post #6 of 9 Old 04-07-2007, 12:26 PM
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if you run different rears at each end, you can drive it in 2wheel, but you won't be able to use 4wd. that could defeat the purpose of your 4wd. gettin' junkyard axles off a 4 popper is the cheapest way to do it. also, you'll be able to do it yourself mostlikely. i would agree with rockworm!
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post #7 of 9 Old 04-07-2007, 12:52 PM
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sounds like a good excuse to swap in 4 banger axles


regear around here is $300 per axle for labor. i dunno about your area.

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post #8 of 9 Old 04-07-2007, 01:11 PM
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Quote:
Originally Posted by red92YJ
That seems kind of high. If I can get the parts for $399 then I would think labor would only be about the same as the parts cost. Am I wrong?
thats why I said "who, what, where".

arround here, labor will run between $300-400 an axle, or $600-800. Add to that your $400.oo for parts and...

shop arround and maybe ya can do better.

btw... just my , but I'd stay away from genuine gear.



WoRM

edit note:
Quote:
Originally Posted by red92YJ
Next dumb question...
Do I need to do the front and rear with the same gearing or can I just do the back?
YES... unless U never intend to use 4wd.

'05 LJR, 6sp, RC long arm w/MC 6" coils, 5.13 D44's w/chromo shafts, MetalCloak fenders/sliders/body armor, 37x12.50 MTR's, Warn 9.5, RockHard swing out w/full spare. <><
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post #9 of 9 Old 04-07-2007, 01:17 PM
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Quote:
Originally Posted by red92YJ
I looked at the chart on the 4wd.com catalog I just got and it was showing 4.11 was middle of the road for my tire size and what I use my Jeep for. They have a special going on gear sets (front and rear) with the master install kits included for $399. Is this a good thing?
Next dumb question...
Do I need to do the front and rear with the same gearing or can I just do the back?




That seems kind of high. If I can get the parts for $399 then I would think labor would only be about the same as the parts cost. Am I wrong?
I'll still get it done because I want the top end power but I was hoping to get out for about $800.
you need to re-gear both axles or you wont be able to use 4WD. Also bear in mind that a re-gear to 4.10s will also require new carriers front and rear as the stock axles have carrier breaks. a 4.10 ring gear will NOT fit on a 3.07 carrier. So you are looking at probably another 100 bucks or so per axle for new carriers if you just want to keep running open diffs. Or you could go with a full carrier replacement locker like a Detroit or an ARB, but those get real expensive real quick. Also, typical labor for re-gears usually runs about 300 bucks per axle, and gears are generally not something you want to try and tackle yourself as the specialty tools involved can get pretty expensive and the tolerances are pretty tight, too much or two little and you will destroy your brand new gears in a hurry

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