Drove my jeep home from teraflex today with the new 5.38's and WOW!!! I like my jeep even better now. Even though its a 15 mile drive home and thats all i've driven it so far I can't give a detailed review but its driving much better now. Almost like a regular car, I was holding study with the cruise on 70 all the way home and the RPM's held right study right at 2700 the whole way. Usually the RPM's were all over the place, up and down trying to find the right gear. It feels like a smoother ride. I'm going camping this weekend so I'll keep track of the improved mpg and report back on the change with that on Monday. I was getting between 12-13.5 mpg with the 4.1's and I can already tell that my mpg is going to be better then that with these 5.38's. My next purchase is either going to be the superchips flashpaq or the AEV pro module thing to fix up the speed calibration and adjust the shifts points with my new gear set up which makes me think I was probably actually really going about 65 on the way home even though my speedo was set on 70 I don't think thats accurate cause I never had my speedo recaliberated after my lift and tires. Anyway, I was originally trying to decide between the 5.13 and the 5.38s and I'm glad I went with the 5.38's already. the new Teraflex differential covers look awesome as well.





Thanks Teraflex!

 

What I don't get is how people know the difference between driving 5.13s and 5.38s when they have only had 1 or the other???? Just an observation

 

I knew you would feel this way. Holding a steady rpm, staying in OD, not downshifting all the time makes the JK a much more pleasant ride. Of course the additional power and is great as is the better fuel economy.

It sound like we have another convert to the "gears are the best thing you can do to a JK" cheering section.

Maybe because we know other people with JK's and have ridden in or drove theirs. Just sayin'.........

 

All I'm saying is the 5.38's with my set up, (35 inch tires) gives me much more power and my jeep drives much better then when I had the 4.1's. Never said I knew the difference between the 5.13's and the 5.38's. I'm sure I'd be just as impressed with the 5.13's on my jeep after driving it how it was for the last 4 months. It just felt like the power wasn't there before. I know the difference between the 4.1's and the 5.38's cause I've had them both now but i never said anything about 5.13's being any better or worse then the 5.38's. I did say I'm glad I ended up going with the 5.38's cause if I ever want to upgrade to 37 inch tires I know the power will definately be there to do that.

 

[QUOTE=chuck45;1097927]
It sound like we have another convert to the "gears are the best thing you can do to a JK" cheering section.
[QUOTE]


Yes, the gears are definately worth it!!!!

 

Gotcha. Good choice either way, you planned for the future since you already know the Jeep will play tricks on your mind and tell you bigger tires are needed. Mine is screaming 44's as we speak

 

So let me get this straight, going from 4.10 gears to the 5.38's and running 35", the JK will get BETTER mpg? Here I thought you would get less mpg's.....

 

You got it straight. The numbers work out like this at 75 mph on the freeway:
32" and 4.10 is 2250 and 18 mpg OD and cruise marginal
35" and 4.10 is 2050 and 14 mpg OD and cruise useless
35" and 5.13 is 2600 and 18 mpg OD and cruise work fine
35" and 5.38 is 2750 and I don't know from personal experience but probably pretty good.

The thing is the OD is .69 which really drops the rpm. Going with 5.13's and 5.38's on an auto with 35's lets the engine cruise at it's peak torque (2600-2900) which lets it stay in OD and lets the cruise work. With the steeper gears you spend LESS time at higher rpms so get better fuel economy and get better power. Fuel consumption really seems to increase over 3000 rpm.

Gears are like magic in a JK.

 

Looking good, congrats and I'm sure you'll enjoy your choice!

 

Looks great, seeing how many people are happy with the performance I think I'll end up going with 5.38s and 35s, in CT we have a lot of rolling hills here so the extra gearing should help quite a bit. Also, isn't the sweet spot of this engine between 2500 and 3000rpm? I think I read that somewhere.