I have a 1998 ford explorer 4x4 4.0 sohc

The car drives and runs great and it drives in forward and shifts fine. When I throw it in reverse it goes but stops like something is binding up. it has the sohc engine but if anyone knows what could be causing this issue please lay in your input. When I bought the car it had the issue so I payed 800 cash for it redid the all the disc brakes and brakes likes it starts and runs fine but I have way to many project cars in my garage and driveway and I am hoping to slim it down a notch. Im hoping to know if this is a trans issue or the rear end so I could do the repairs and get it sold or use it to do some towing. Please any info will be greatly appreciated.