A sliding window assembly for a vehicle includes a window frame having a top rail portion coupled to a bottom rail portion by side rail portions. The top rail portion has a shorter length than the bottom rail portion. A fixed window is attached to the window. A sliding window is mounted in a sliding sash. The sliding sash is moveable relative to the fixed window. The sliding sash includes a top sash portion coupled to a bottom sash portion by side sash portions. The top sash portion has a shorter length than the bottom sash portion. A removable track assembly is attached to the top rail portion. At least one bearing is attached to the top sash portion of the sliding window sash. The at least one bearing is slidingly engaged with the removable track supporting the sliding sash over an entire travel range between open and closed positions preventing tilting of the sliding sash relative to the window frame.