Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of September's Ride of the Month Challenge!
1 - 5 of 5 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter · #1 ·
I recently acquired a 2012 JK Unlimited. I put 275/70/18's on it, with a 2" spacer lift. It previously had the 255/75/17's. It has the 3.21 rear end. It now feels sluggish. I don't offroad much. What would be the appropriate gearing for daily driving? Also, if I have the gearing changed will it affect the durability of the differentials. I hate to mess with it since it is new.

my speedo is 2 mph off. I know I can get a programmer to fix this. Does anyone know how this is currently affecting the mpg reading on the digital display. Is my mileage actually better or worse than listed?
 

·
Registered
Joined
·
4,136 Posts
The programmer will do more than correct the speedometer. It will also correct the shift points for the transmisson. With the 3.21 gears, you are not going to gain a lot though. Gear changes, if done correctly, will have no impact on the differential durability. It's the larger tires and activities off road that would impact that.

Bob K.
 

·
Registered
Joined
·
1,738 Posts
Check out the gearing chart to see what your highway RPMs will be with the various gears.

For your tire size I think 4.56 would be about as short as you'd want to go. If you're ever planning on going to 35's or higher then you may want to take that into account and go even shorter.
 

·
Registered
Joined
·
2,979 Posts
If you're going to stay with your current tire size, I'd do 4.10s if I were you. That way you'll still be able to hit interstates without listening to your engine scream for help.
 
1 - 5 of 5 Posts
Top