John Dezso Ratzenberger (born April 6, 1947) is an American actor, voice actor, and entrepreneur. He is best known as Cliff Clavin in Cheers. He is also known for his extensive vocal work in Pixar Animation Studios' films, notably Hamm in the Toy Story franchise and Mack in the Cars franchise.

Based on this passage, who plays the voice of mack in cars? Let's think fast. Stream of consciousness:
The relevant information to answer the above question is: He is also known for his extensive vocal work in Pixar Animation Studios' films, notably Hamm in the Toy Story franchise and Mack in the Cars franchise. So the final answer is John Dezso Ratzenberger.