What gear ratio to choose?

Jeeps and anything with little engines, run the lowest gears you can possibly stand.
I went from 4:56s to 5:38 and my little four banger became much more usable.

 

Percival has the original (albeit a fresh rebuild) 4 cyl with 5.38s and the Warn OD. I'm swapping the axles for 4.27s next week. I have to run at least 1 1/2 hrs on the highway to get to where I need to lock the hubs. If you trailer a jeep to go and run through the woods, or live in the woods, then the 5.38s are the way to go. With the 5.38s, if you spend any time on the highway (at highway speeds), overdrive is a must and even then you are limited to 65 MPH unless you like to really wind out the engine - I think @ 65-70 you are turning 3100+ rpm with 15" tires. That's on a motor that redlines at 4K. Yes, the jeep will go faster - I've had mine over an indicated 75 MPH - but I would rather not have to rebuild the engine frequently.

A good friend that has clocked over 300K on his '64 CJ5 tells me when he was young and stupid, he was rebuilding the engine every 18-20K because he drove the jeep at 3100+ rpm all the time. When you keep the RPM down around 2400, the problem goes away . . . there is a reason willys/kaiser went from having the axle ratio go from a 5.38 standard/4.27 optional to 4.27 standard/5.38 optional

Just something to think about-

Eck

 

It will mostly be a trail Jeep. It'll get driven around here some. Maybe to the store and back.

 

4.88 would work if they weren't so hard to find.