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Discussion Starter #1
What I'm about to ask is probably the most asked, and beat up question of them all, and I feel like a shmuck asking. :banghead:

Gearing.

I've read forum, after forum, after forum, and page after page of info, looked at 3 gearing charts, and I am still waffling real bad between my choices.

I'm re-gearing a 09 JK, Manual 6-speed with 3.21's, and the largest tire I'm going to have on there sits 32.5" mounted (BFG KM2 255/80/17). I cannot for the life of me decide between 4.10 and 4.56. For what I do, I'm not sure that I need something as deep as the 4.56, but I've read that difference between 3.21 and 4.10 isn't impressive either.

I only drive the jeep on the weekends, since I have a company vehicle, and I drive 1-3.5 hours to get to my camp/fishing/4x4 areas. The trails I take are anything from tame fire roads to nasty black diamond switchbacks covered in loose rock and 2-5' boulders. I'm MORE than impressed with the Jeep in 4 low, but I am not impressed with it on the highway or in town. I'm really looking for the best of both worlds here guys.

Can I get a seat of the pants reaction from you guys with similar setups?

Thanks everyone, and sorry for the repeat question. :surrender:
 

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I'd go with the 4.56 gears. Although 4.10 will be enough, for the same amount of money you can have 4.56 and get a little more power. That will be nice if you ever tow anything or if you go to a heavier 33" tire. You could even do 35" tires If you want. As long as you stay with light weight tires it won't be too bad with a 6 speed. 4.10's just don't seem worth the money. You want to regear once and do it right and I think 4.56 and your 6 speed will be plenty for your 33's and even some light 35's
 

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Discussion Starter #6
I'd go with the 4.56 gears. Although 4.10 will be enough, for the same amount of money you can have 4.56 and get a little more power. That will be nice if you ever tow anything or if you go to a heavier 33" tire. You could even do 35" tires If you want. As long as you stay with light weight tires it won't be too bad with a 6 speed. 4.10's just don't seem worth the money. You want to regear once and do it right and I think 4.56 and your 6 speed will be plenty for your 33's and even some light 35's
Yeah, I got an f-350 for the towing, but I would like to use the jeep to haul the dirtbikes on a few day-trips... That's a good point you have there, thanks. Having said that, one thing I worry about is whether or not I'll gain the use of 6th, but lose 1st.

For you and anyone else, how is the mileage at 27-2800 rpm?
 

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I have a 2012 with the pornstar engine and stock 32" wheels. I did some mpg/rpms at different speeds awhile back and posted it on JK-forum. Clearly the 3.8L engine is going to be a bit different, but it might give you some feel for how the gearing affects MPG. Basically over 65mph and the MPG starts to drop fast. Here's the cut and paste job.

This is not exact but the best of my testing ability and memory(I didn't have a smart phone back then). They are all 6th Gear on very flat 1-65 Indiana interstate.
80mph - 15.5 mpg - 2750 RPM
70mph - 17mpg - 2400 RPM
65mph - 19mpg - 2200 RPM
45-55mph - 22mpg - under 2000 RPM
I personally would go with 4.10's max if your driving it much on the interstate. Shifting between gears is pretty quick with 32" wheels. Especially between 1st and 2nd. I would guess with 4.56 you would end up skipping 1st on pavement, or not getting the clutch out between 1st and 2nd. If you can find a used rubicon at carmax or somewhere to test drive that would maybe help give you a feel for it on pavement.

Offroad I would guess both would be pretty nice.
 

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4.56 gears are harder to find at least in good quality gears. Even those that list them are usually out of stock. I started to get them for mine and found them only in so so gears. I got 4.88 but in a Auto and sort of love them and sort of hate them. For towing my camper they are great and I can turn over the tires from a dead stop but on the highway they make me wish I had not went that low. One of the reasons that I am going to 35's for my next set of tires. The 33's are just not cutting it for ,y 4.88's

The great thing about a 6 speed is if you need the extra power you can just go down to 5th gear and stay out of 6th for towing. I would say 4.10's IMO but 4.56 want be that bad either if your running 35's
 

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Discussion Starter #11
You guys have great points. I'm leaning in favor of the 4.10 since its mostly street/highway that I'm wanting to improve. The jeep is already extremely capable off-road, I guess I just really need to decide if I'm ever going to go up to 35's. Although, the jk is a little portly and I don't like the idea of making it wider with tires and spacers, especially on a few of the trails where I'm climbing rock gardens while barely clearing pine trees on both sides.

Thanks again, appreciate it!
 

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I would without question stick to 4.10 if I knew that 255/80 was the largest tire I'd ever run.
 

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I agree on 4.10. On 32s 4.10 is very slow while offroad and very friendly on the road. From the type of driving off road that you mentioned, I doubt you will want to use your low range very often even with 4.10
 

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$1600-2000 for a regear. Trade in for a Rubicon that already has 4.10's??? Thought crossed your mind?

As for me, I have the 3.8 and an Auto tranny, running 5.13's :)
 
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