Nicknamed "Mumbles", Tremel batted right-handed, stood 5 feet 11 inches (1.80 m) tall and weighed 180 pounds (82 kg).

Tremel started the 1955 season in the minor leagues but was recalled to the Cubs in July, and posted an MLB-career-best 3–0 record and 3.72 earned run average, with two more saves, in 23 games.

He made the Cub roster at the start of the 1956 campaign, but in his only appearance, April 27 against the Cincinnati Redlegs at Crosley Field, he gave up three hits and an earned run in one-third of an inning.

He was a mainstay in the Texas circuit and with Shreveport, spending all or portions of seven of his 11 pro years with the Sports.

After retiring from baseball in 1959, Tremel spent 31 years with the SKF corporation in Altoona, Pennsylvania.