The side note part caught my attention. I plan for this to be more of an overland rig (Like theRubicon etc) than straight obstacles but I want to be able to go at them and have a decent shot. The 700r4, 4l60, 4l80 etc, what has better gearing but also can be made to be manual valve body and what shifters do people like to use and why?
I am pretty sure all can have manual valve bodies... I have lokar shifter in one rig and art carr/winters in the other. I would lean you towards the Art carr, its quicker, easier.
Novak used to have the best knowledge base to check/research ratios on the tranny. It seems like the 700R4 spread was something like 3.06, 1.73, 1, .75.
I would start with your distance drive ratios, the speed you want to go at what RPM for the tire size you want to run, then work backwards. So for example- 70 mph on 37" tires at 2500 rpm at what ever your overdrive ratio is.
That will give the ratio you want in your axles. From there you can could determine which low range ratio or T-case options to get to a crawl ratio you want to crawl/wheel with...
I am pretty big fan of a spread sheet to consider the options.
Lot of crawlers tend to gear their axles a little too low for highway travel, I think Tcases and axle combos are a better options for lower gears, but then again I run a 4spd Atlas, so I have lots of low range options.
let me know if this makes sense.