I see a lot of threads about 35s, Auto, and 5.13s. I have seen the RPM chart as well. I have searched quite a bit but cannot seem to find info on 33s, Auto, with 4.88s or 5.13s that also factors in mpg.

I have 285/70R17 Duratracs, an Auto with 3.73 gears. Around town performance does not bother me, but the highway performance is awful. 90% of my driving is 70-80 mph, as my daily commute is 55 miles all highway. I get about 15 mpg.

What would be the best gear choice (4.88 or 5.13) in this scenario to either keep the same mpg, or raise it a bit (if possible). I will be staying with 33s. I know it is not a Prius, but if I could stay at 15mpg or better that would be great while improving highway performance.

 

I would say to go ahead with the 5.13s as long as you are sure that will not put anythi g smaller than 33s. That way if you do go 34 or 35 later you will be alright. You will still be in acceptable range for 33 inch tires. Maybe try the superchip flashpack for now? ??

 

I would love to, but it will not be compatible with the 2011s until April/May

I come from a 5.3L V8 and am a self proclaimed lead foot. I knew going in I was not going to have the same power. But if I can spend a little bit of money to improve the highway driving while retaining fairly respectable (15+) mpg, I am all for it. I guess my main worry is, with 5.13s, an Auto, and 33s, my RPM will be pretty high. What kind of fuel consumption will I see, worse, same, a little better? If it is worse, I will get 4.88s and take my chances.

 

Since you have 33's you are close to the factory Rubicon tires which use 4.10 from the factory and gets around 17-19 highway. For the best mileage you want the highest gear with the lowest RPM but still be in the power band. So you should be looking at the tallest gears, lowest numerically. 4.56 would probably be your best bet but I understand they are hard to find.

From the project JK site there is a quote from installing the 4.56 gears with 33's:

"I have been running 33″ tires from about the 100 mile mark on my JK. This given, I didn’t think that there had been much of a difference between the stock 32″s and my 33″ tires. Now with the 4:56 gears, I realize that there is a difference. I now have more power in every gear. I don’t find my self having to downshift while driving through the hills at freeway speeds. These gears are much better for cruise control. My biggest surprise though, is the increased effectiveness in second gear. The JK has a low first gear, and it needs it. First gear driving is not practical for trail driving, however. When trail driving with the 4:10’s I found myself having to downshift from second gear most any time that I came across anything technical, rocky, rutted etc. Basically If I had to drop my speed below 6 miles per hour, I had to downshift to first gear. I’m really pleased with the new flexibility of second gear. On a trail this weekend, I was able to drop down to 4 MPH, in a fairly technical section, without having to downshift to first. Call me lazy but, I’m really stoked on how the 4:56 gears have improved my trail driving experience. For anybody running 33″ tires, the 4:56 gears are the perfect solution.

Brett (aka - Woods)" Under Jeep JK New Products: project-jk: superior-axle-jeep-jk-wrangler-456-gears-are-here

 

Sounds like to me that the individual in the write up has a manual. Me personally like the power of driving 70 at about 2600 or 2800 rpm for highways that arent particularly flat. At these rpms i get about 17.5 mpg and love the fact that i can pass and maintain a speed above 70 with out feathering the sknny pedal. That is just me.

 

I would definitely go with 5.13 gears with the auto.....I have 5.13's with my 35's and auto and if I had a rubi with a front Dana 44, i would have gone with 5.38's.

Are you currently driving with O/D off? That will help significantly on the hwy....no superchip's a drag though.

When I had 35's, which measure 33.75", and 3.73 gears, I ran O/D off and was up around 2800 rpms on the hwy going 70...drove great (except for long inclines) and i was getting 15 - 17 mpg on long hwy trips...although I also had the superchip.

Now with 35's and 5.13 gears and O/D off, I'm running pretty much as the charts dictate and holding about 2450 rpm at 70 but inclines don't stop me now. my hwy mpg's now remain around 15 mpg....maybe 16 on a longer trip.

 

5.13 may sound low but in an auto it really isnt. Keep her in a rpm that she doesnt have to downshift and the mpg will be ok but 5.13 gears on 33s and the power will nice. Im puttin them in and still have 32s. Will be getting 35s but cant gear any lower. If i could I would.

 

First before you re-gear, try purchasing a Superchips flashpaq and see if this helps improve your highway driving and adjust your shift points.

If the superchips does nothing for you and the BIGGEST tire you are (ever) going to be getting is 33's then I would look at the 4:88's. However, if you think you will be going to 35's or bigger down the road...then 5:13's! Also, when considering gearing are you having any plans of adding a locker? This will be the time to purchase that locker & get it installed at the same time you are re-gearing.

 

I don't believe the Superchip is available for the 2011's yet.

For the 6-speed yes, 4.88, but for the auto, even with 33's, I would go 5.13. Like I mentioned before, I would have gone 5.38 with 35's.

 

I won't argue...don't have a auto.