Converting to manual steering..Confused

mguner said

You should be able to pull you shaft out to engage the manual box. Grab the shaft where it slides into the outer portion with visegrips and tap with a hammer.

Click to expand...

I did this once on a '74 Dart. The manual steering box I had already had the coupler on it. I just tapped my column down using vise grips and a hammer. It worked fine, however, I always wondered how much splines were left before it pulled out. If someone could answer that question, then I would be more at ease, because I had to tap it down approximately 3 inches.