Good to know, I never knew tire size would affect the 4wd like that. My tires always match but still very good info to know.

Now thats being a good neighbor and she may turn out to be a good friend when the SHTF.

I have a neighbor who lives about one mile down the county road. She has a nice homestead up on the side of a mountain, chickens, ducks, hogs, cattle, rabbits and a huge veggi garden. Her ingress to get to the property is about 600 yards long and winds up the side of a mountain. She has a tough time driving up her dirt driveway in the wet winter months so she bought a Ford 4WD half ton pick up truck to make the trip easier. She came over the other day complaining that the 4WD would not function, it wouldn't shift into all wheel drive and if she shifted with the engine off it would go, but pop out of 4WD as soon as she started to drive away. I went over to look at it and noticed it had oversized tires on the rear axle and small street tires on the front of the vehicle. This was the reason the truck wouldn't work in 4WD as all 4 tires have to be the same size and rotate at the same RPM while in the 4WD mode. If the front and rear tires are a different diameter the transfer case gears will be unable to function at the correct ratio and it will pop out of 4WD or burn up the transfer case in short order. She ended up buying 2 new mud and snow tires and after installing them the 4WD works fine.