I just put 37" (actual 35.5") on 2005 6MT 4.0 TJ and have been learning about re-gearing requirements and little confused about the recommendations online. First, to get few details out of way:
1) this car is never going to leave paved city road, never off-roading, almost never highways, etc...
Ok, So after a couple hours of searching... I have come up with no definitive answer. I see threads full of opinions, but no facts.
Here's the setup...
I have a 2001 TJ Wrangler Sahara.
4.0 and 5-speed manual.
It has a 4" rough country suspension lift.
I'm running BFG 31x10.50-15's.
I was researching which tires/sizes I could/should run on my Jeep and found several places that had essentially this same chart for tire sizes and gear ratios combinations. I found it interesting. I'll let others decide if it's interesting or helpful to them...
For those still trying to decide on which transmission that they should go with maybe this information will help.
The Gear Ratios in the 5 Speed are:
1st - 3.77
2nd - 2.16
3rd - 1.41
4th - 1.026
5th - 0.81
Transaxle Ratio - 4.12 ('07); 3.91 ('08)
This calculates out to 15.53:1 in low and 3.33...