James Diefenthaler, 70, of rural Elkhart Lake died Wednesday morning April 8, 2026. He was born in Kiel, son of the late Willard "Lefty" and Dorothy (Schulz) Diefenthaler. Jim graduated from Kiel High School.

From an early age, Jim had a passion for cars, motorcycles and racing. Best known for owning and operating his full service machine shop, Diefenthaler Auto Machine and Jet Engineering. Jim jumped into the race world when he started drag racing right after high school. That evolved into building countless engines for car enthusiasts and especially race car teams. He formed many great friendships in the racing world and was known to visit the tracks to talk to drivers and crews so he could understand their needs and performance changes they wanted to make. He built a reputation for building fast, reliable engines for the local race circuits. Jim was the first to give credit to the drivers and crews for his success, always saying it was a team effort. In his free time he enjoyed building and working on his own cars and motorcycles.

Survivors include his sister; Marjorie Klunck, brothers; John (Nancy) Diefenthaler, Tom Diefenthaler, nieces and nephews; Rick (Amy) Klunck, Jason Klunck, Christopher (Andrea) Klunck, Carrie (Adam) Krull, Peter Diefenthaler along with many great and great-great nieces and nephews. Jim had many friends and customers throughout his career. Jim's family wanted to thank some of the closest, Jim Stamfel, Randy Kiel and Tim Lefeber for the lifelong friendships and all the help they have given in the past years.

He was preceded in death by his parents; step mother; Jean Diefenthaler, brother-in-law; Robert "Geno" Klunck.

A time of gathering will take place at Meiselwitz-Vollstedt-DeTroye Funeral Home on Saturday April 18, 2026 from 10:00am until 12:00pm. Burial will follow in the Schleswig Cemetery. A celebration of his life will immediately follow the burial at the Altona Supper Club (2306 Calumet Dr. New Holstein).