The manual transmission has a much wider gear spread (3.83 first to 0.79 overdrive) than the automatic (2.80 to 0.75). With the deeper first gear, they can get away with the 3.07s and still be driveable around town while benefiting from the lower RPMS on the freeway to get better mileage. The automatic with the 3.55's gives you a balance between in town driving and highway mileage.

As far as which gears were more common for a given axle, it depended mostly on what options were available from year to year.

4 cylinders used the Dana 35 mostly so you see more 4.10's being in the 35 than the 8.25. Beyond that, a vast majority are going to be 6 cyl automatics with 3.55's with it being a crap shoot whether they have the 35 or 8.25 axle under them. A distant second is manual 6's with 3.07's. The rest are probably just single digit percentages of the overall production totals.

 

So basically I just got lucky? I know that it's weird but would a 5 speed off roader be a good possibility if the aw4 in the collision jeep is garbage?

 

Sounds like you got lucky.

The auto vs manual debate can rival religious or political discussions sometimes. A lot of it is affected by what kinds of trails you frequent. Do you do more mud bogging, dirt trail riding, or rock crawling? How extreme do you get?

The automatic tends to be easier but some enjoy the challenge and control of the manual.

I've wheeled both. I like either, so long as they're set up right.

My JK has the 6 speed manual and at first it really wasn't all that great. 3.21 gears and a 2.72 transfer case with an engine that has no low end torque meant I stalled. A lot. When I went to 35's, I put 4.56's in. It was better on road but didn't have enough crawl ratio for serious rocks. And then I moved from low elevation flyover country to the mountains and it got worse. After having no luck finding a Rubicon transfer case for the 4.0:1, I saved up enough to get the 4 speed atlas with 2.72/4.3/11.7 low ranges. Now I can really crawl without fear of stalling my engine and I can finesse my way through obstacles that most other people bump and bounce through. I love it.

However, my XJ is still the AW4 automatic with the 2.72:1 t-case. I put 4.27 gears in the grand wagoneer axles I swapped in to go with my 31" all terrains and it really does pretty well overall here in the mountains too. Sure, I don't get the slow crawl but it does great on the trails I take it to. The torque converter does really make it easier to manage at low speeds and keeps it fun.

 

In terms of mudding I've been up to my frame in the Chevy, I've been fording up to the hood, and for rock crawling I haven't really done any rock crawling before so not sure, keep in mind the Chevy weighs 6,200 and has a 3.08 one legger