Its fairly accurate with 37's, 6 speed and 4:10 gears

 

It's not right according to the table. According to the table he should be at about 1900 RPM, unless he actually has 3.71 gears (which is what I think he was getting at) or his tires are actually measure closer to 29" instead of 33".

The table seems to be accurate to me. I have "35's" on a 2012 JKU auto with 3.73 and I'm turning around 2100-2200 at 70 MPH; however, my Goodyear Duratracs (315/70R17) actually measure a tad under 34", so the RPM's listed on the table seem accurate in my case.

 

Well, I can't speak for him but I'm turning 305/65 17's which actually measure about 32.25". At 70 mph I spin right at 2100 rpms.

 

That's exactly what I was getting at. Just measured and they are actual size 32.75". So, in my opinion, I either have 3.73 or the chart is wrong.

 

So the chart is wrong then. Otherwise turning 2100 at 70 with 3.21 you would be running about 29" tires.

 

I'm not claiming the chart incorrect, just giving my real world experience. I will be regearing to 4.56's regardless of rpm. And will eventually bump up to 35's, but for the time being I'll stick with the 305/65 17's, 3.21's auto JKU.

 

I'm just trying to figure out if it's the chart or I possibly have 3.73's.

 

Yep... definitely sounds like the 3.21 gearing column might be off then. This is probably the type of feedback the OP was looking for. Could be a simple formula mistake assuming he used an Excel spreadsheet to create the table.

 

Yup, think I will be going with the 4.56 when I regear te axles on my 2012.
I've heard a 2012 with 3.21 gears running 35s is no problem, sounds like the tranny handles quite nicely.

 

What ratio is the consensus so far on 37's?