The 23-year-old spent two seasons at Whaddon Road after a successful long-term loan spell from Portsmouth, establishing himself as a firm favourite with Robins fans.
He made 132 starts and 13 substitute appearances, scoring 16 goals, helping Mark Yates’ side reach the play-offs for two seasons in succession before joining City in the summer of 2013.
“I wouldn’t say my time at Cheltenham was the making of me because I have not achieved anything yet,” Pack said.
“But it was a stepping stone for me, shaping me into the player and the person I wanted to be and I will always be thankful to the fans and people at the club for that.
“It was great for me and I have fond memories of my time there.”
Pack was back at Whaddon Road for a pre-season friendly in July, which Bristol City won 4-1.
He joined the action as a late substitute, having just undergone surgery to remove wisdom teeth.
“It was a strange one for me with the tooth saga, but I was lucky to be able to play in some capacity,” Pack said.
“This match will be different, being competitive and in front of the TV cameras, so I would love to play a part.”