Detroit,What year is your truck. More than likely you broke an axle.If your truck is a '49, or later, it has the floating axles. Just remove the axle cover from each side, & pop the end of each axle with a large hammer.The axles will pop out, & you can inspect them. The 4100, & 4400 trucks,are 1 1/2 ton trucks,& would have come originally, with a single speed rear axle.They won't interchange, with a 2 speed axle.