effective crawl ratio is 50% of whatever the physical first gear is....the torque convertor creates that difference.
SO, if your first gear is 3.5, your t-case is 2.5, and your axles are 4.1, then...
(3.5 x 2) x 2.5 x 4.1 = 71.75
IMO, the disadvantage of the auto is downhills - reduced compression braking, tho a LOW stall convertor can make a big difference.
