What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)

I have a 1999 Jeep Sahara with a 4.0 a Dana 35 a 3.07 gear ratio and a 32 RH 3 speed auto transmission the Tranny has been built to with stand any punishment that I would ever dish I out.
I have a 2 1/2 inch lift. I will not be rock crawling I will be in sand and on logging roads with some light to moderate wheeling in the sand and mud. I have 31’s on it. I would like to go to 32’s maybe 33’s from the chart above it looks like your recommendation is to stay with the 32’s but the chart does not show my combination of Tranny to engine to gear ratio . I see biilebobs post and I like what I see. Do you agree with biiliebobs post it seems to be pretty thorough based on good experience.
 
Firstjeepbuild said:
I have a 1999 Jeep Sahara with a 4.0 a Dana 35 a 3.07 gear ratio and a 32 RH 3 speed auto transmission the Tranny has been built to with stand any punishment that I would ever dish I out.
I have a 2 1/2 inch lift. I will not be rock crawling I will be in sand and on logging roads with some light to moderate wheeling in the sand and mud. I have 31’s on it. I would like to go to 32’s maybe 33’s from the chart above it looks like your recommendation is to stay with the 32’s but the chart does not show my combination of Tranny to engine to gear ratio . I see biilebobs post and I like what I see. Do you agree with biiliebobs post it seems to be pretty thorough based on good experience.
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If you want 32s or 33s, go with 4.10 gears. If you want to stay with 31s, 3.73 is you your best bet.
 
my 2cents, I am running 32s on my 06Lj with stock gearing and the 42RLE auto, stock is 3.73 and I am right at the sweet spot on the highway..70 to 75mph I'm between 2000 and 25000rpm...5.13 gearing for 33" tires seems way to deep for a daily driver...I am going up to 33's eventually and then maybe 4.88 gearing.
 
James Brewer said:
my 2cents, I am running 32s on my 06Lj with stock gearing and the 42RLE auto, stock is 3.73 and I am right at the sweet spot on the highway..70 to 75mph I'm between 2000 and 25000rpm...5.13 gearing for 33" tires seems way to deep for a daily driver...I am going up to 33's eventually and then maybe 4.88 gearing.
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Eventually you’ll realize there are much better sweet spots.

would you care to guess the difference in rpm between 5.13 and 4.88? Surely you don’t think it’s so much that it would make 5.13 way too deep and 4.88 perfectly reasonable?
 
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James Brewer said:
my 2cents, I am running 32s on my 06Lj with stock gearing and the 42RLE auto, stock is 3.73 and I am right at the sweet spot on the highway..70 to 75mph I'm between 2000 and 25000rpm...5.13 gearing for 33" tires seems way to deep for a daily driver...I am going up to 33's eventually and then maybe 4.88 gearing.
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Your sweet spot leaves a lot to be desired.
 
machoheadgames said:
Eventually you’ll realize there are much better sweet spots.

would you care to guess the difference in rpm between 5.13 and 4.88? Surely you don’t think it’s so much that it would make 5.13 way too deep and 4.88 perfectly reasonable?
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Please enlighten me, what is the sweet spot for 70-75 mph for 42rle auto 4L???
 
James Brewer said:
Please enlighten me, what is the sweet spot for 70-75 mph for 42rle auto 4L???
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Regardless of transmission, 3k at 75mph is a nice goal to aim for.

33" tire
42rle/31.5”/3.73=2059rpm @ 75mph
42rle/31.5”/4.10=2263rpm @ 75mph
42rle/31.5”/4.56=2517rpm @ 75mph
42rle/31.5”/4.88=2694rpm @ 75mph
42rle/31.5”/5.13=2832rpm @ 75mph
42rle/31.5”/5.38=2970rpm @ 75mph
 
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jjvw said:
Regardless of transmission, 3k at 75mph is a nice goal to aim for.

33" tire
42rle/31.5”/3.73=2059rpm @ 75mph
42rle/31.5”/4.10=2263rpm @ 75mph
42rle/31.5”/4.56=2517rpm @ 75mph
42rle/31.5”/4.88=2694rpm @ 75mph
42rle/31.5”/5.13=2832rpm @ 75mph
42rle/31.5”/5.38=2970rpm @ 75mph
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So... as tall as possible just like every other 42lre recommendation 👍
 
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Alex01 said:
So... as tall as possible just like every other 42lre recommendation 👍
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Lower than most would ever expect. This is for a 31ish", which suggests that even the Rubicon with an auto was undergreared from the factory...

42rle/30”/5.13=2973rpm @ 75mph
 
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@Jerry Bransford i have an 06 4.0L, 42rle and 3.73 gears (stock) dana 30/35 axles. recently installed a 3.5” metalcloak suspension lift with 33” pro comp mud tires. 4th gear(od) is mostly useless here in the hills of east texas. jeep previously had 31” tires and 33’s killed 4th gear(od) 31’s were ok with 3.73’s. not planning on any hardcore rock crawling or the such. need to be able to do 70-75 on highway and still be good offroad. what gears are recommended for my setup? no real plans to jump to a bigger tire. at 56 i have enough of a time saddling up so to speak after a motorcycle accident( broke leg). thanks in advance for your input sir.
 
For 33's and a 42RLE, nothing less than 4.88 but 5.13 would be ideal. Either of those will produce ideal highway rpms, I personally would go 5.13. With either of those you'll actually see an improvement in your mpg. Mine went from sub-12 mpg to nearly 15 mpg after I regeared my TJ with 35's from 4.88 to 5.38. And even with 5.38 even a few more rpms on the highway would be nice.
 
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Jerry Bransford said:
For 33's and a 42RLE, nothing less than 4.88 but 5.13 would be ideal. Either of those will produce ideal highway rpms, I personally would go 5.13. With either of those you'll actually see an improvement in your mpg. Mine went from sub-12 mpg to nearly 15 mpg after I regeared my TJ with 35's from 4.88 to 5.38. And even with 5.38 even a few more rpms on the highway would be nice.
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thanks again for your input sir.
 
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txbemis69 said:
thanks again for your input sir.
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will have to suffer with poor gearing for a bit as i gather funds. thinking about new complete axle assemblies dana 44 from east coast gear supply. possibly over building it but, better safe than sorry.
 
txbemis69 said:
will have to suffer with poor gearing for a bit as i gather funds. thinking about new complete axle assemblies dana 44 from east coast gear supply. possibly over building it but, better safe than sorry.
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Installing a Super 35 kit into your rear Dana 35 will eliminate the need to upgrade it to a Dana 44. The Super 35's 30 spline 1541H shafts are even slightly stronger than the factory Dana 44 shafts are.
 
1999 Jeep tj with a 32 rh and a 4.O Daily driver, 2 1/2 inch lift , I have 31s now but would like to go to 33’s if it wont cause problems the way my Jeep is built. I do not rock crawl. I drive sand in the desert as well as mud and snow in the mountains of eastern Washington. I am have 3.07’s in my rear end I am intending to install a super 35 kit. What if anything should i or can I do for the front Dana 30. At this point both front and rear end are stock and in good condition.
 
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Firstjeepbuild said:
1999 Jeep tj with a 32 rh and a 4.O Daily driver, 2 1/2 inch lift , I have 31s now but would like to go to 33’s if it wont cause problems the way my Jeep is built. I do not rock crawl. I drive sand in the desert as well as mud and snow in the mountains of eastern Washington. I am have 3.07’s in my rear end I am intending to install a super 35 kit. What if anything should i or can I do for the front Dana 30. At this point both front and rear end are stock and in good condition.
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For the driving you mentioned stock shafts should be just fine. The main issue is when you start hoping the rear end and the tires find grip.

https://wranglertjforum.com/threads...angler-tj-lj-and-other-re-gearing-faqs.17063/
 
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