JLight,
I am sure your dad based his rules on his experience. However, I have had no power train problems with a 1949 Dodge Power Wagon, 1953 Willys 1/2 ton pickupa 1974 Jeep 3/4 T pickup, a 1985 Nissan 4wd King Cab pickup, or a 1995 Dakota V8 4wd from 1966 to present running steel chains on all 4 wheels when needed. It gives more traction and spreads the stress more evenly from front to back axles. They are never run on dry pavement or over 35mph, usually below 20 mph. I have pulled JD 4010 size (7,000# to 8,0000#) tractors on solid ice that didn't want to start in the cold, pulled wagon loads of feed in muddy conditions that stuck a 2wd farm tractor with chains, pulled out town kids trying out their new 4wd, and similar off road (usually) farming situations. I have often used chains on one end of a 4wd pickup if that will do the job, but usually on the front because in our terrain and soil types, it allows you to steer the heavy end of the pickup. We usually need them on both ends (all four wheels) here. They are no substitute for a tractor, but in limited traction conditions will often outpull a 2wd tractor
with chains that weighs twice as much. All this heavy a use of 4wd chains certainly taxes the power train, but even the 85 Nissan with 218,000 miles on it has not broken
any power train parts. The biggest bother to me is mounting and removing chains on all 4 wheels. Sometimes once they are mounted, they stay on that vehicle here on the farm all winter.