Ok since everyone seems to be asking gear questions here's mine.

I hav an 08 rubicon umlimited auto and am about to install a 3.5" RE superflex lift. The original plan was to run 35's but I am certian 37's will end up on it eventually. I was planning on installing 5.13's but was wondering if anyone has actually thrown in 5.38's and could post their pros & cons.

So the question is.

Should I stick with the 5.13's or have enough people installed 5.38's to prove they are a reliable option for a JK?

Thanks

 

i would do 5.13s they would be great for the street and because you have a rubi your t case is 4.1 making you plenty low for offroading.

 

I've got 5.13s and 40" tires. In fact the other JKs on here running large tires most all run 5.13 gears. The 5.38s seem to be seperated from the 5.13s by only a few hundred RPMs, so the difference isn't that much. Plus I heard that the extremely small pinion gear on the 5.38 is just waiting to get chewed up from running large tires (much like the rest of our Jeep).

 

I'd say the above advice is pretty decent coming from guys with the experience of running their setups

 

I cant imagine what a Dog the JK is with 40's.... Is it your DD?

Your right, the crawl ratio is really low, In moab I found myself in 3rd or 4th gear between the rocks

 

Oh heck no! I drive a car day to day (38 mile commute) plus I don't think my clients would appreciate climbing on all fours trying to get into it while wearing a business suit

I don't think I would ever recomend 40's for a DD since depending on your commute distance, you'll eat up alot of expensive tire, burn through alot of gas (<$2/gal ain't bad right now though) and have little power off the line. Push it down to 37's and now we may be talking. It is surprising though how much power was restored when I added the Gibson exhaust, intake and TBS. I definitely didn't buy the Jeep for it's on-road performance

 

Auto, and 37" I would go 5.13. You will be fine.

 

Thanks for everyones responce. I had settled on 5.13's until 5.38's started showing up again. Looks like I should stick to the original plan and throw the 5.13's in.

Thanks

 

I think a portion of that is because of the lack of early availability of 5.38s for the JK. As for the pinion, they should be pretty close one to the other, both 8 tooth and same spline count, but not like I've seen them side by side.

Also interesting you mentioned the relatively small rpm difference between 5.38s and 5.13s as there are a lot of people that would act if their nuts just got smashed by a hammer if you were to suggest the same from 5.13s to 4.88s which have about the same 5% difference.

 

The best quote so far.


I have a 6spd. Would that change any of your opinions?

I have stock tires on my rubicon and in Moab I found that I wanted a slightly lower first gear. In my TJ, with a STRAIGHT 6 (I miss that motor), I was able to idle more without feathering the throttle up the steap stuff. I was thinking 5.13s with 35s would give me that little extra but 5.13s with 37s may not be enough.

Who makes 5.38? I do not think superior or dana has this option.