Trim pork loin of excess fat, season with salt and pepper. Set aside.
Heat a large pan over medium-high heat. Add oil, once the oil is hot, add the pork loin and brown on each side for about 2-4 minutes or until golden.
Add the pork to the slow cooker, rub with garlic. Add soy sauce and pineapple chunks with pineapple juice to the slow cooker. Distribute the brown sugar evenly over the top of the pork.
Put the lid on the slow cooker and cook on low for 4-6 hours, for a soft pork loin, that can still be sliced.
NOTE: If you want the pork extra soft, to make shredded pineapple pork, cook it on low for 8-10 hours, making sure during the cooking process, to lift the lid a few times and using a ladle pour the juices over the pork in order to keep it moist. After you shred the pork, add it back to the slow cooker and cook it on low for another hour.