no noise during neutral coast rules out stuff at the corners (bearings, wheels, big tires, dragging/faulty brake components) as those items are either rotating or almost in contact with rotating items while the rig is coasting or powered. You've got some components not found in most scouts...your range box and your divorced t-case. I know you've had the case inspection cover off for a visual and didn't see anything amiss. What about the range box? I'm just curious as to why you're most suspicious of the transmission. From my outside looking in perch, I'd be casting my suspicion more towards your non-stock gear boxes and associated drive shafts. There's actual gears and teeth in those boxes. Yes, there are rotating parts inside the auto trans, but pressurized hydraulic fluid is doing most of the work.