5.13s will work nicely with 38s

 

i too am fixin to regear my machine. i have the automatic and 35's. i was thinking of going with the 4:88, but now im thinking 5:13. what rpm's would i be runnin at 70 mph with each? i live in louisiana and im thinking of maybe going on some jeep trips in the future, so i wanna be able to do some interstate driving as well as do some wheel'n.

corey d

 

I only knew the rpms from experience but I would recommend the 4.88s with 35s in an auto. The best I could do is get my friend to tell me what his is running at. He has an auto with 5.13s and 37s.

 

Its only a 300 rpm difference between 4.88 and 5.13

 

I can't agree with that at all. I have an auto with 35's and at 75 spin 2600 rpm. I would much rather have the rpm 100 to 200 rpm higher. I have never encountered anybody with 35's and an auto who installed 4.88's who didn't wish they had gone with 5.13's.

There is no valid reason to go with 4.88's on an auto. The only reason that begins to make sense is fuel economy but I get the same 18 mpg on my very heavy rig (see sig - and I always keep a full tool kit, spares, and lots of recovery gear in the Tuffy drawer - and RockHard stuff is beefy and hell for stout) as I did on it when it was a dead stock Rubi with 32's and 4.10's.

Hell, if I was doing mine again, and now that 5.38's are available, I'd probably go with 5.38's. Then maybe I'd get 19 mpg!

4.88's do make sense on a stick with 35's; unless you plan on going to 37's. As far as I know 4.56's aren't available and would not be cost effective as there isn't enough change to justify the bucks.

 

4.56s are available and if you want your engine screaming by all means go for it. I was stating from mypersonal experience and highway driving they were to tall. They were great in the trails but when I use it as a DD for 6 days and wheel 1 day out of the week I rather have it set up better for the road. No one put a gun to his head I am just telling him what I have experienced. My gear selection wouldnt be for gas mileage it would be for overall performance. If your want fuel economy you have the wrong vehicle.

 

4.56's became available this past summer-fall, we now have the following gears available.

4.10
4.56
4.88
5.13
5.38

They finally got around to getting them all out.

 

i drive mine mostly on the highway, but i also want power when off road. i want to be able to drive long distances on the interstate and not be screaming. i know right now my average fuel milage is showing 12.9 or something like that. i gotta get more miles per gallon. it doesnt feel like its straining to turn the 35's, but i guess it is.

corey d

 

I was getting 13-14 with 35's and 4.10's before I got my 5.13's. At 75 mph my rpm was 2050. With 5.13's my rpm is 2600 and I get 18 mpg. So now I have power AND mileage. If I went with 4.56 or 4.88 I would have less power and less mileage; which is like not having your cake and not eating it either.

4.10's were steep in the old days of non-OD tranny's (both auto and stick). Don't let old notions of what used to work color your notion of what works in a JK. 2600-3000 is not a lot of rpm for a high reving, marginally sized motor in a heavy vehicle. .69 is a deep OD ratio and 35's are big tires.

 

chuck,
did you reprogram your computer? im ready to get my gears changed as soon as i can settle on which gear i wanna go with and who to let do it, but now should i start thinking reprogramming?

corey d