Known for being one of few individuals to be part of Grey Cup and Super Bowl championship teams, he was a key figure in the development of the single-stanchion goal post.

After graduating in 1942, he entered the U.S. Navy, marrying Patricia before being "shipped out," to the South Pacific spending the next three years in the service during World War II.

Entering the 1955 NFL season, the Eagles were expected to strongly challenge the defending champion Browns, but when the team fell to 4–7–1, Trimble was fired on December 12.

Trimble was not out of work long, accepting the head coaching position of the CFL's Hamilton Tiger-Cats on December 29, signing a one-year deal.

After losing out to Vince Lombardi for the Green Bay Packers head coaching job in January 1959, Trimble endured continued frustration in three of the succeeding four CFL campaigns when Hamilton lost in the Grey Cup, each time to Winnipeg.

Shortly after his dismissal, Trimble allegedly assaulted Montreal Star sportswriter Ian McDonald, but was able to avoid any trouble by apologizing to the journalist.

During his CFL career, he gained a nickname, "Jungle Jim", in part for his reputation in making controversial statements that spurred his running feud with Winnipeg.

During a scouting trip in British Columbia with former player Dave Skrein, who recalled a play where the receiver caught a ball down the field only to hit the goal post.

As he related later, "I came back after the game and was sitting around with a friend of mine, Joel Rottman, and we were talking about the double posts and wondered why they couldn't be changed.

Then Cedric Marsh, a British engineer for the Aluminium Corporation of Canada stationed in Montreal, developed the single post to be strong enough and we patented it.

The so-called "slingshot" goalposts, named because of their "Y" shape, were adopted by CFL in 1966 and by the NFL in 1967, just after Trimble returned to coaching as an offensive line assistant with the New York Giants.