Gear Question, which do you prefer?
 

OK, have an 07 Unlimited Rubicon AUTO. Went to 295/70R17 tires and killed my mileage and power (obviously). Now, making the move to 35's FINALLY and going to re-gear my diffs (Yea!)

Wondering, 5:13 OR 5:38??? It is my daily driver, I was pretty happy with the way it drove with the stock 32's and I got about 20 MPG on the highway. I'm a commuter so I do a fair amount on the freeway. With the tires I went to, I dropped to 14 MPG and it sucks to drive on the street.

Just looking for personal opinions from those of y'all who have 35's and 5:13's and 5:38's. Looking for:

Do you think the RPM at 70-75 on freeway is too high?
general MPG on highway and combo?
Similar to stock in performance, yes or no?

Thanks for your time and input. I'm leaning towards 5:13's but curious about the other too; definitely want to make the right choice.

THANX!

I am on the fence between 4.88's and 5.13's. I know everything say's 5.13's for 35's, but most tires are not a true 35". I do very little hwy driving, so the power around town with 5.13's would be nice, and am looking at tires that run closer to a 35" as to say a Duratrac, KM2's which both i like, but run closer to 34's.

FAQ's --> Drivetrain section --> RPM charts

Use 'actual' measured tire heights.

Auto, 3.73, 31" tires (guessing on actual height of stock 32's) =
1953 rpm @ 70

Auto, 3.73, 34" tires (guessing on actual height of 35's) =
1781 rpm @ 70

Auto, 3.73, 34" tires --> OD OFF
(1781 / .69 =)
2581 rpm @ 70

Auto, 5.13, 34" =
2450 rpm @ 70

Auto, 5.38, 34" =
2569 rpm @ 70


Soooo,
35's with 3.73's and OD Off = 35's with 5.38's and OD On

Drive with the 35's and OD Off and see how you like the performance. Good as is, go to 5.38. If you want lower rpm's, go 5.13. :dontknow2:

5:13
 

I'm leaning towards 5:13's. I've driven one with 4:88's and it feels sluggish like mine after I put 295/70R17's on it. Definitely going at least 5:13 but maybe the 38?
Thanks.

Thanks
 

THANKS for the numbers; good comparison. What tires & gears are you running???

3.73's and 32's (stock)
3.73's and 295/75/16 Terra's (32" actual)
5.13's and 295/75/16
5.13's and 315/75/16 Bighorns (33.5" actual)
5.38's and 315/75/16



The 295/75/16's were a big mistake, should have gone straight to 35's.
The 5.13's were good at the time, got them back before 5.38's were available for d30's.
The 5.38's were a good upgrade over the 5.13's, but they were part of a front PR44 swap. Probably would not have made the ratio change if the 30 did not bend.
:D

auto tranny and any tire larger than 33's you gotta go with 5.38's. I did and love them with the added power and mpgs. When I had 4.10's it was way too sluggish going up hills/mountains and my mpgs were around 10 :gak: Now I get about 14-15 city and 17 hwy

I have an 09 auto, lifted, bumper, 35" tires etc and if you want to keep the rpm 's down on the hiway I'd stay at 5.13 that's what I have and I like it and with a superchip I'm happy with the gas mileage.....just remember it ain't going to be a speed demon even if you choose 5.38 it's a jeep :)

I'm a 70 MPH guy anyway, no leadfoot here. Thanks for the info. Just curious, what superchips program are you using and what's your average MPG? I have a superchips and really couldn't tell the difference between 91 or 87.
Thanx!

Thanx, I'm leaning that way!