JustClaire is incorrect, on a tbss torsion style center diff (nvg120 transfer case) you cannot simply pull the front shaft and get 2wd. The torsion unit will not apply power to any of wheels if there is no front shaft. Basically if you do this your truck won’t move.
Our t case is entirely mechanical, but effectively becomes an open diff when either the front or rear drivetrain is disconnected. Just like how a Torsion style rear diff works, you pick one tire up you get nothing on the other side. Ours is just split front to rear not left to right.
If you want selectable 4wd/2wd you can use a stock trailblazer 4wd transfer case.
Our t case is entirely mechanical, but effectively becomes an open diff when either the front or rear drivetrain is disconnected. Just like how a Torsion style rear diff works, you pick one tire up you get nothing on the other side. Ours is just split front to rear not left to right.
If you want selectable 4wd/2wd you can use a stock trailblazer 4wd transfer case.