Here's the setup:
2002 4.6 automatic 117k miles 3.55 gears in 8.8 axles
6" fabtech 16x10 A.R. rims 35" BFG AT's
4" CAI w/flowmaster single in dual out
According to the "gear calculator" to match stock power settings I should change the gears from 3.55 to 4.56. Now I drive a total of 90 miles a day to and from work, and sometimes 50-100 miles while at work, (luckily the company pays for that part).
I flat tow my International Scout II to different places and such for the more hard core wheeling, and towing a regular size boat every now and then to the lake. Long trips would be elk hunting in Colorado, and bay fishing/ snow skiing.
I would think that 4.88's would be a better bet for towing, but how much of a difference would they make on my milage as a daily driver? Plans, include getting a power programmer later, and maybe a supercharger way down the line. I don't think I'll be going any bigger with the truck as far as lift goes but if I did it would stop @ 38.5's with a 3" body lift (yeah right...)
So the question remains 4.56,4.88, or 5.13? Thanks.

 

Where do you drive at? If you drive a lot of roads with 65 mph or 70 mph speed limits, I'd go with 4.56 gears. If most of it is 55 mph zones, 4.88 would probably be a good choice since you tow a lot.

 

Mostly Texas highways, 60-70 usually. Lots of stop and go during the early morning, late afternoon. Would the gears require a carrier change in the 8.8's? I know my Scout II had to go from a series 3 to a series 4 carrier in the Dana 44's with the 4.88's. I put the thick ring and pinions in the front, which required no carrier change. Of course they didn't tell me that when they did the rear axle. That's why I did the front.