the truck is running but won't move back tires are spinning

What is your question?

started the truck and the truck is running. placed the truck in drive and tried reverse but don't move but hear the back tires spinning. Tried later that day and truck move and ran fine. was driving and stop at a stop light, heard a pop sound and truck wouldn't move but could hear the back tires spinning. After about 15 -20 mins it moved.

How long has your 2000 Mazda B3000 had this problem?

started two weeks ago