The way I see it, about anything that requires lube for any kind of metal to metal contact you should do a break in at least a little. Although you could probably get away without one.

 

I'm running 35's w/3.21's on a 2012 with a manual and 6th gear is useless unless I'm going downhill !! At 70mph, RPM is 1600 and has basically no power even on flat ground... personally a re gear is a must if you want to use 6th gear. I'm waiting to re gear mine after I hear a little more feed back on here... I'm leaning towards 4.88's.

 

With 35s and 5:13s I'm at 2,400 rpm at 60 mph in 6th gear. I probably could have gone with 4:88s and been perfectly happy and probably saved a little on mpg. But I went with the 5:13s so I could go up in tire size without having to regear again. I've still only got 50 miles on it since the new gears so I'll report back after the break in period to give a full report.

 

That was my experience as well. 4:88's would probably be sufficient for 35s. I went with 5:13's because I believe I will go up to 37's eventually.

 

Just curious, but what is first gear like? I've had some cars with steep rear gears that ended up coupled with transmissions with a steep first gear - which basically rendered first gear useless. I've always tried to gear so that sixth is just an overdrive gear, one that you go into and out of only above 60 mph coupled with rpm's below 2,000 rpm.

 

I have 4:88s and am spinning a hair over 3,000 at 75mph. If I was planning on a true 37 (38) I would have gone 5:13s. It's a big difference coming from 3:21s, but if I had 3:73s or 4:10s I might have been hard pressed to switch with anything under 37s. The ECO light is almost always on now and and idling/rolling speed is much faster. I can idle in and out of parking spots now, where I used to have to give it some gas when the wheels were turned. In 4LOW I can idle over logs 6-8" tall (haven' tried bigger, but likely need to tap the gas). If you have an auto, the new trans does a great job managing things so the difference probably is not as apparent as with pre-'12 autos. I also was getting a locker put in so I figured while we were at it.....

 

HMMM, I am pretty sure my Jeep starts in 2nd now unless I select 1st manually -- either that or it's shifting out of first quickly. You can do a 0-40 pretty fast in an overweight Jeep if that's your thing by staying in 1st. It's comfortable, but for daily driving I let the trans do the thinking. On the highway I definitely am into 5th by 50mph, and there is plenty of range left for a leisurely pass. Punching it drops you to 4th with more than enough gear to get you to 70mph fast and w/o issue. I would assume that there will be new version of the ProCal tune to modify things as well as other tuners. Pedal response lag is also more apparent when there is more torque on hand........it's a process. I am happy as is, but I will continue to seek improvement.

 

That answers that. Worthless first vs. worthless six - flip a coin. Actually the end result of a worthless first is then no overdrive on the top side and the mgp hit.

 

Here's a quick video of me on the hwy.

4.88's
35's
procal

http://static.photobucket.com/player...-25-34_206.mp4

 

2012 JKU auto with 3.21 gears in top gear with 35" tires:

30 mph = 767 rpm
40 mph = 1023 rpm
50 mph = 1279 rpm
60 mph = 1535 rpm
70 mph = 1790 rpm

2012 JKU auto with 3.73 gears in top gear with 35" tires:

30 mph = 892 rpm
40 mph = 1189 rpm
50 mph = 1486 rpm
60 mph = 1783 rpm
70 mph = 2080 rpm

2012 JKU auto with 4.10 gears in top gear with 35" tires:

30 mph = 980 rpm
40 mph = 1307 rpm
50 mph = 1633 rpm
60 mph = 1960 rpm
70 mph = 2287 rpm

2012 JKU auto with 4.88 gears in top gear with 35" tires:

30 mph = 1167 rpm
40 mph = 1555 rpm
50 mph = 1944 rpm
60 mph = 2333 rpm
70 mph = 2722 rpm

2012 JKU auto with 5.13 gears in top gear with 35" tires:

30 mph = 1226 rpm
40 mph = 1635 rpm
50 mph = 2044 rpm
60 mph = 2453 rpm
70 mph = 2861 rpm

2012 JKU auto with 3.21 gears in top gear with 37" tires:

30 mph = 726 rpm
40 mph = 968 rpm
50 mph = 1210 rpm
60 mph = 1452 rpm
70 mph = 1694 rpm

2012 JKU auto with 3.73 gears in top gear with 37" tires:

30 mph = 843 rpm
40 mph = 1125 rpm
50 mph = 1406 rpm
60 mph = 1687 rpm
70 mph = 1968 rpm

2012 JKU auto with 4.10 gears in top gear with 37" tires:

30 mph = 927 rpm
40 mph = 1236 rpm
50 mph = 1545 rpm
60 mph = 1854 rpm
70 mph = 2163 rpm

2012 JKU auto with 4.88 gears in top gear with 37" tires:

30 mph = 1103 rpm
40 mph = 1471 rpm
50 mph = 1839 rpm
60 mph = 2207 rpm
70 mph = 2575 rpm

2012 JKU auto with 5.13 gears in top gear with 37" tires:

30 mph = 1160 rpm
40 mph = 1547 rpm
50 mph = 1933 rpm
60 mph = 2320 rpm
70 mph = 2707 rpm

I used this gear calculator http://www.grimmjeeper.com/gears.html and selected the Dodge NAG1 for the 5 speed auto.