I have just bought a 98 f-150 with 185000 miles on it. Motor runs great,trans,shifts great. Then come the 4x4 first someone had broke the vacuum lines that go down to the front axle. So came on here did some research and found that then line where on wrong,so fixed them front axle seems to be working correctly as far as when I but the switch in 4x2 the front drive shaft moves freely. Then when 4x4 the drive shaft locks as it should but have no power to front wheels. Then can stop truck put N and back into D and wow power to the front wheels, but then as I roll seems like truck starts to bindup in the drivetrain. Had truck jack up all 4 up and mark the tire made one rotation and the front seem to make 2 turns to 1 turn in the rear. So check front tag on diff need to write them down but the #355 was on the tag and rear of the truck is a 3.55 ratio. Need help cant figure out whats going with this truck. Will get tag # and put on here. Front diff has been changed found #on it from salvage yard.