I just got a 2008 wrangler X about a month ago and I wanted to figure out what gearing I should go with I have 33's 18 inch rims and I want to still go 70+ on the freeway and still able to do some pretty good rock crawling

 

You will get tons of opinions, from what I've read 4.88 is a low as you want to go with a Dana 30 without the risk of breaking the RP.

However tons run 5.13 and are very happy.

For 33s 4.56 or 4.88.

 

If you have a auto go with the 513. I have stock 32 inch rubber on 18 inch wheels and went 488, and if I could do it over again it would be the 513. And I have the sahara with the Dana 30 in front and a 11 auto with the mighty (NON TICKING) 3.8 power house. I can run 80 mph all day long at about 2800 rpm. 70 is about 2500 rpm which is a good cruise rpm for the 3.8. But with anything bigger then the stock 32 inch rubber you need at least 5.13. If you want to go 35 inch rubber you need at least 5.38 or you are just waisting your money. You can get a 5.38 for the Dana 30 now I have been told. The 3.8 auto will perform great if you gear it right. And look mom no ticks. So glad I ordered a 11 and didn't Wait for the junk Jesus motor. I almost waited but ordered the 11 instead. 22K on her and never been back to jeep. 75 year old mechanic did the gears and I do everything else.

 

How is your mileage with that setup?

 

About 16 around town, and 16 to 20 on the highway. At 55 it will make 20, and at 80 more like 16. But better then with the stock 3.73 gears I had in it. Overdrive was pretty much worthless with the stock gears and any wind or any grade at all. Ran in third gear most of the time, and some days I would just turn OD off, to avoid that constant shifting or hunting between gears. Pulls overdrive solid now. About 2000 rpm at 60, 2500 at 70 and 2850 at 80mph. With a tail wind at 70 mph I have made 22 mpg. Bucking a 35 mph wind at 70 mph will drop you down to about 14 to 16 mpg, but it will pull it in overdrive now. And it gets up and goes from a standstill a lot better now. More power in every gear, at any speed. Drives like a whole different animal!

 

That's very strange, because if you get better mileage with 4.88 gears and stock tires, then why not put these gears in there straight from the factory? I constantly get 14-15 mpg around town with stock 255/17 tires and 3.78 gears (auto/2dr). Highway I can get around 19-20 at 60mph. This mileage is hand calculated, not computer calculated.

It's normal to downshift on uphill drives.

I find it perfectly fine, as long as you're not going uphill.

No doubt more power. I just can't understand how your mileage could improve.

 

I would of got 4.88 or 5.13 from the factory, but jeep is not smart enough to offer a good gear combo. This was for the 07-11 auto JK's. In the 12 model they took care of this problem, and with the new 5 speed auto the 3.73 has a final gear ratio the same as the old 4.88s like I have. The new 4.10 is about the same as the old jeep with 5.38 gears in it. The OD gear in the old 4 speed auto was way to fast, hence no power or rpm. The new 5 speed is way slower, hence more rpms which equals more horsepower. And the 3.8 is more in it's sweet Eco spot at 2000 rpm at 60 instead of 1600 rpm at 60 mph. Regear and you will love it. Best mod you can do for any auto 7-11 jk. Worth every penny! Cheapest horsepower you can find in the jk. Just a fact.

 

What's the junk Jesus motor the 2012 or 2010 ?????

 

Question, I picked up a 07 rubicon/ unlimited , how do I know what factory gears are installed or do they all one with the same? If so what are they, I'm running 255/70/17 BFG's so I'm assuming as long as I keep that set up I'll be just fine, your saying if I run 35's then 5.38's are the way to go? Thanks

 

I have a auto BTW