There are gears inside the transfer case that are in different positions for 4WD and 2WD. In 2WD they are positioned so they only send torque to the rear wheels. When they're in 4WD, they send torque to all four.
Our reference does not list a 1.9L engine in the Hyundai Santa Fe. The smallest is a 2.4L. You have an all wheel drive system that can be in either Auto or Lock. In Auto Mode the system will automatically send torque to all four wheel when it senses that the rear wheels are slipping. In Lock Mode, torque goes to all four wheels. If you go above about 30 MPH, it switches back to 2WD automatically to prevent damage to the system. I have attached a couple images that can help you visualize this.
Images (Click to make bigger)
Monday, August 8th, 2016 AT 6:43 AM