Steering column dis-assembly

Rebuilding my ‘74 Challenger steering column. So far so good with basic tear down but I’ve run into a hiccup. It’s a column shift auto. How do I get the shift tube off the steering shaft?

EDIT,
remove the shift lever to access the counter sunk set screw. Just loosen it a tad and the collar should slide right off the tube

No experience with one that new here either.

If I remember right (on a '70) the column gear shift handle has to be removed for access to the set screw.

Already removed shift lever and set screw. Collar was pressed on the shift tube. Took some taping with a mallet to get collar off the tube. Now, how does the tube come off the steering shaft or vice-a-versa? At present, it does not slide off. There is an obvious seal at one end, but it has no apparent tabs. A small diameter wire spring presses into this seal and seats against a large diameter wire snap ring looking device. There is no apparent grooves for this snap ring, but at around .180 in diameter, it’s not going to be easily spread . It will spin on the shaft, but won't spread open without a pretty monster set of pliers. The upper tube is flopping around on the shaft.