I was trying to back up in 4 wheel drive and the left rear wheel was spinning and the right was just setting there. Is something wrong ?
Does the explorer have a limited slip differential ? on 2002 Ford Explorer Sport Trac
Some did have limited slips diffs, but it sounds like yours does not. If yours does have limited slip and the one wheel spinning while the other side is not, I would expect to feel a vibration from the clutches in the differential slipping. If you do not feel any vibration, it probably does not have limited slip. To check for sure ask a dealer, use the id tag on the driver's door,(or door jamb) check the code where it says axle, with that code and the VIN#, they should be able to tell you the equipment level.