Kenny's father decides to install the True Tone AB-700, the "Ultra-Glide," in the Brown Bomber after Byron's latest episode of troublemaking. Byron's bad behavior spurs the Watsons to decide to take him to stay with his Grandma Sands for the summer (and possibly the next school year); this means a long family road trip from Flint, Michigan, to Birmingham, Alabama.

Daniel Watson puts a lot of time, energy, and money into improving the car before the trip; he eventually purchases the "cream of the crop" drive-around record player so that the family can listen to their favorite records without the needle scratching the vinyl when the car goes over bumps. This new addition impresses everyone in the family, except for Momma, who is worried about the expense. She is tremendously pleased, however, when her husband plays her special song on the Ultra-Glide: "Under the Boardwalk." The family sits in the car for two hours listening to music on the special player with its second speaker... until they finally reveal to Byron that he is being taken away to Alabama to straighten out his act.