It will go into gear with driveshaft spinning but rear tires will not

Yes, this happens when the drive nut and hub spine strip out on one side. Here is an exploded view and how to take it apart. Please upload images of any questions you have. There are many places that make aftermarket parts of this jeep and the rear end they use in many vehicles so you should be able to get parts for it. Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.