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Discussion Starter · #1 ·
hi,

i am looking to regear my jeep since i read a lot of good things on it on this forum. my questions are

1) does it worth regearing if i keep the stock wheels and tires ?

2) what gearing ratio should i use knowing 1) ?

thanks !

pat
 

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What year is your jeep. If it is prior to a 12 model like my 11 sahara 2 door I would go 5.13 and that will work great with stock tires and even a little bigger also. That is about as low as you can go in a Dana 30, but right where you need to be even with stock tires. What year is your rig anyway? It's probably not a 12, as a 12 with 3.73 and stock tires would be ok and you wouldn't be thinking regear!
 

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Need to know year and whether you have an auto or manual transmission.
 

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Discussion Starter · #5 ·
my rig is a 2011. i want the 2012 so bad but cant afford the trading cost.. so i was looking to regear to obtain decent highway behaviour

also will regearing affect the shift points and addressthe poor eco mod downshifting
 

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so i was looking to regear to obtain decent highway behaviour
A regear will do that.

also will regearing affect the shift points and addressthe poor eco mod downshifting
You'll also want to get an AEV ProCal to "tell" the jeep about your new gears. That will adjust the shift points.

also does regearing have a similar effect as driving with o/d off ?
Sort of. But you'll regear in such a way (by, for example, getting 5.13s) that you'd never be able to "duplicate" by merely turning off the OD.
 

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Discussion Starter · #12 ·
thanks for all the info !!! i might regear my auto to 5.13 . .. last question .... will regearing void the tranny warranty ?
 

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thanks for all the info !!! i might regear my auto to 5.13 . .. last question .... will regearing void the tranny warranty ?
Nothing but odometer tampering really "voids" any part of your warranty, the issue is whether your warranty would "cover" a given transmission or other problem that arises after the regearing.

That's going to be a mixed factual question (what happened and what went wrong) and legal question (how your warranty coverage applies). So really all anyone can do up front is form educated opinions.

For a discussion of that with regard to regearing, check here: (http://www.wranglerforum.com/f33/regearing-and-warranty-127442.html)
 

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Am I correct that the charts above only apply to 2WD or 4WD-HI? For example I'm in the yellow with a 2012 JKUR with 35s and 3.73 gears. The chart's "mild trail use at low elevation" suggestion wouldn't apply when I throw my Rubi into 4WD-LO---dropping my gearing by a factor of four, right?
 

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Am I correct that the charts above only apply to 2WD or 4WD-HI? For example I'm in the yellow with a 2012 JKUR with 35s and 3.73 gears. The chart's "mild trail use at low elevation" suggestion wouldn't apply when I throw my Rubi into 4WD-LO---dropping my gearing by a factor of four, right?
The numbers show the RPMs at (I believe) 65 mph. That would of course be in 2wd on the highway or other high speed roadway.

The color coding provides guidance to help you choose gear ratios based on your use of the Jeep--i.e., under performing gearing, moderate gearing, and high performance gearing.

However, the truth of the matter is that for the 3.8 engine (which would obviously have different numbers in the RPM calculations) you would always want to regear yourself into the high performance area. The 3.6 has a more power and more room for error, so I could see rationalizing deliberately gearing yourself into the moderate area.

That said, if I was going to bother regearing either the 3.8 or the 3.6, I'd put it in the high performance zone.
 

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The numbers show the RPMs at (I believe) 65 mph. That would of course be in 2wd on the highway or other high speed roadway.

The color coding provides guidance to help you choose gear ratios based on your use of the Jeep--i.e., under performing gearing, moderate gearing, and high performance gearing.

However, the truth of the matter is that for the 3.8 engine (which would obviously have different numbers in the RPM calculations) you would always want to regear yourself into the high performance area. The 3.6 has a more power and more room for error, so I could see rationalizing deliberately gearing yourself into the moderate area.

That said, if I was going to bother regearing either the 3.8 or the 3.6, I'd put it in the high performance zone.
Right (except the RPM numbers are for 70MPH, but you got the right idea). All makes sense. I just don't want to spend $2K or whatever unless I absolutely need to do so. My logic may be off, but the characterization of the yellow for my situation---"mild trail use at low elevation"--seems to be an overstatement or oversimplification.

IMO, unless I'm missing something, if the chart was to have anything to do with operating in low range at any elevation (which is the mode in which you always do rock crawling), it, at minimum would need to have different color codes for Rubis versus non-Rubis--if I am correct that the non-Rubi's 4WL transfer case drops the ratio only by a factor of 2.72.

Also, since the difference in 3.73 to 4.10 gears is 9.9%, another way to look at it, if I am correct, is that my 3.73 dropping into low range would operate the same as a Jeep with the same tires and 4.10 rear gears that had a 3.64:1 4WL transfer case gear ratio. (4.10/3.73 = 0.91 = 4.0/3.64). That's still much better than most vehicles, including the Saharas and Sports, which have a 2.72:1 4WL ratio. The FJ only has a 2.57:1 ratio.

Also, I can't find the numbers, but didn't the new 5-speed auto tranny lower the first-gear ratio? If so, that would make a difference in the off-roading gearing, as you're mainly worried about being low enough in first gear I think.

Another way to look at it is that the crawl ratio for a Rubi in 4WL with 4.10 rear gears and the auto tranny is 58.8:1 (if my calculations are right). So, for A Rubi with 3.73 gears, it still is a very-low 53.6:1, which ought to be adequate for just about anything I could do anyway. By comparison, the FJ has a crawl ratio of 33.8:1 (with auto tranny), and has a less-powerful engine.

I was really worried when I put my 35s on, that my Jeep would be sluggish, but it just ain't. I think maybe that the 4.10s and the 32s maybe are just a little too low for me. For example, when I first started driving my Jeep with the 3.73 gears and stock tires, I would, unintentionally spin my tires from a start when trying to merge onto a highway with fast traffic near my house, which caused the traction control to kick in. Now, with the 35s, that never happens, essentially giving me better traction on the street from the start. It might be partly because the new tires grip better, but I think it's mostly because of the higher "gearing" with the 35s. If I went to 4.10s or even lower, I might be back to spinning my tires when I barely hit the Pentastar.

Anyway, others' valid preferences could be far off from mine, but my '12 JKUR with 3.73 gears and 35" tires seems about perfect for city and highway driving. And I can't imagine the 53.6:1 crawl ratio will let me down with that set-up. I'll find out next week after I get my replacement drive shaft put on and head out to the hills.

Anyone feel free to correct me, if, as is possible, I'm missing something important.
 

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Also, is the chart based of an avg? because my stock tires, 29" im running approximately 2700 rpms at 70 mph.. which puts me in the 4.10 gear range, but i have a 3.73 gear
 

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c0d3x5 said:
Also, is the chart based of an avg? because my stock tires, 29" im running approximately 2700 rpms at 70 mph.. which puts me in the 4.10 gear range, but i have a 3.73 gear
Chart might be for 65 mph . . . I don't have a 2012, so I can't be sure. Your speedo could also be off. And of course make sure you're looking at the right trans.
 

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Also, is the chart based of an avg? because my stock tires, 29" im running approximately 2700 rpms at 70 mph.. which puts me in the 4.10 gear range, but i have a 3.73 gear
That's curious. Do you have auto or manual?

The 2012 chart seems to be a 2012 analog to the pre-2012 chart (post # 4), which specifically says "70 MPH Range." The 2012 chart seems to hit me (35s, auto, & 3.73) right on the money at 70 mph. It says 2,081 RPM. My tachometer reads roughly 2,100 (it's just a needle) when my speedometer says 64-65 mph (but my tires are 10% larger, so I'm really going about 70 mph). So, I think it's a 70 mph standard.

I'm not trying to be critical of the charts, but it is based on 6th-gear manual and 5th-gear auto gear ratios at 70 mph.

It has nothing to do with the fact that, in 6th-gear, the manual is higher than the auto in 5th-gear, but in 1st-gear, the manual is (to the contrary) lower than the auto; or that the Sahara/Sport have 2.73:1 4WL gearing; while the Rubi has 4:1 4WL gearing.

In short, I think the chart can give you some idea of what's good for fast highway speeds. (For me, with the 285 HP, my 3.73 at appx. 2,081 rpm does great, and can downshift to 4th when necessary, but rarely needs to).

In any event, to really distiniguish between capabilities to do "mild trail use at low elevation" and "rock crawling at higher elevation" (claimed in chart at post #4), I think you'd need a chart that actually looked at actual crawl ratios in 4WL.

Can a 285 HP engine with a crawl ratio of 54:1 do rock crawling at 12,000 ft above see level. I have done so with less than that. But, regardless, the chart does not really address that even though it says it does.

Just my $0.02.
 

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Here is an updated chart that I found for the 2012. It has a legend on it to help identify the type of driving that you want to do. The tire size listed in the chart is the actual tire diameter, not the advertised diameter that is stamped on the side of the tire. I have 35x12.50R17 tires, but they measure 34" in diameter mounted on the Jeep. For people that don't have their tach running close to the chart numbers, consider your actual tire diameter. With my tires and 4.10 gears, my tach is running pretty close to the chart at 70 mph.

JK 2012 Gear Axle Chart.jpg
 
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