Hi,

I'm from Australia and new to this site... I drive a 2007 Jeep JK Wrangler unlimited 3.6l V6. I have a 2" lift and 35" tyres... Should I o for the 4.88 or 5.13 diff ratios?

Cheers!

 

I would probably go with the 4.88, but then again, I drive on the freeway alot...

 

If you have a manual then go 4.56s or 4.88s. I have 37s with a a 6spd and the 4.88s are perfect. If you have an auto then that seems to be a different ballgame. Would say from what I've read atleast 4.88s if not then 5.13s.

 

Thanks for all the replies.... I did want to go 5.13 but the jeep guys here in Australia are saying that we gave more highways here and that the Americans uses it more for Rick climbing etc.... Hence the recommendations for 5.13.... He also said that 5.13 are weaker the the 4.88... Would that be right???

I do have an auto. I do drive on highways and average km per hour would be 80km/h or on freeways 100km/h.... But I also do tow a caravan....

 

Unlimited + automatic + 35" tires + towing = 5.13

 

Welcome to the site!

Gear recommendations vary by transmission. I have an automatic transmission and 35s and just regeared to 5.13. I love it.

IMO, the "art of the science" is to pick the gears that generate enough RPMs at highway speeds for your automatic transmission to not frequently flash out of overdrive/downshift in order to maintain speed.

If you live in a relatively flat area that doesn't frequently get headwinds, 4.88 might be enough, but it'd be a gamble IMO. Seems like around here, virtually everyone does 5.13s (for an automatic).

Edit: I see you're towing. With the extra weight, the extra RPMs generated by the 5.13s would probably be of benefit.

 

Double that

 

Even without the towing, 5:13's with 35's and an auto. 4th gear is still pretty tall, glad I didn't go 4:88

 

I have a 2011 JK automatic. I put in 4.88's. Great on the highway and around town. In Texas we have 80MPH speed limits on some of our freeways and that is why I went with the 4.88's. However, in wind, on hills and loaded down with gear, as others have said, down shifting is still a problem. I have never had 5.13's but would appreciate a few less downshifts that they would bring. I would have liked to ride in a jeep with 5.13's before I decided as I would still prefer less downshifting. Ride in somone elses if you can. Ultimately, the box shaped body and the 3.8L is the problem.

 

Yes, as you go higher (numerically) the gears get weaker (especially in these front D30's). More of an issue for 6spds than auto's, but if you like to bounce through rocks, strength is worth considering.

But for on-road driving, is <70 rear wheel HP enough for you to maintain speed? 5.13's will bring the rpm's up by about 100, which brings the HP up a bit and let's you hold OD longer before downshifting. Not a huge increase, of course, but every little bit helps.

See Post #33 here for a good read. Has graphs and everything...
https://www.jk-forum.com/forums/show...=1#post2147185