Thanks for your reply toytech.Currently I run a 4.0l, 5 speed on 33's with 3.07 gears and I can tell you it's good on fuel but won't crawl on the trails. I am now putting a set of YJ axles (30/35) with 4.10's in with Aussie lockers front and rear and a disc brake conversion on the rear.
I agree with Kunker that you should check out Truck No More. What he built is awesome and I was amazed when he told me he didn't know how to weld when he started!
Would you have an idea how 31's would perform on gravel roads and trails with 3.07's?
I used a calculator from Currie Products website which calculated 31's with 3.07's increases the ratio to 3.51's.
I am interested in following Kunkers advice to view 'Truck No More' build up and will do just that for sure.
Your reply was really helpful.
I have read that driving to the trail head on the highway is were most of the kilometers add up and only a fraction is driven on the trails I guess.
I would consider 3.91:1 swap in my D35 D30's with a Aussie up front but am reluctant to invest until I see how the YJ performs and what mechanical problems arise.