pull
輓 centers on the action of pulling, especially pulling a vehicle or heavy load.
輓 combines 車 (vehicle) with 免, which likely contributes the sound and may relate to the idea of pulling or drawing. The exact historical development is uncertain.
A vehicle (車) with a component that looks like a person bending forward (免) suggests pulling a cart or carriage.
For バン, imagine pulling a van with a rope: van -> バン, and the vehicle (車) is being pulled.