What is the significance of he word "listen" in chapter 12 of Grapes of Wrath?

Can you please quote the sentence for me?

Listen to the motor. Listen to the wheels. Listen with your ears and with your hands on the steering wheel; listen with the palm of your hand on the gear-shift lever; listen with your feet on the floor boards. Listen to the pounding old jalopy with all your senses, for a change of tone, a variation of rhythm may mean—a week here? That rattle—that’s tappets. Don’t hurt a bit. Tappets can rattle till Jesus comes again without no harm. But that thudding as the car moves along—can’t hear that—just kind of feel it. Maybe oil isn’t gettin’ someplace. Maybe a bearin’s startin’ to go. Jesus, if it’s a bearing, what’ll we do? Money’s goin’ fast.