Along with the rebuilt No. 4000, formerly 3002, the Burlington Route's shops built a second streamlined Aeolus in 1938 using a boiler supplied by Baldwin Locomotive Works. The new locomotive received the number 4001. She was the only CB&Q Hudson to have a Worthington feedwater heater instead of the Elesco type, and all driving wheels were of the Boxpok disc type. In this photo from the collection of Carl Weber No. 4001 poses at St. Paul, Minnesota on July 4, 1939, with one of the CB&Q's shovel-nose diesel units. There is some activity around the front coupler of the diesel, which was normally recessed, suggesting that No. 4001 is about to couple to the shovel-nose unit as substitute power for a train in the Burlington Route's Zephyr fleet.