What could be the cause of a awful squeaking noise in the back, driver side tire

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. This sounds like it could be due to brake system components making a resonating noise. Have the braking system pulled apart and all components inspected closely, make sure shims and rattle clips are placed in the proper places and are in good condition, make sure the pads are original equipment in quality and fitment, and make sure the brake rotors are machined properly. Reach out to a shop near you if you need help -- https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.