Steering Column removal

With it in the car not sure? If you wrap the shaft with some electrical tape then clamp a pair of vise grips on it and wack the vise grips with a hammer.
Personally I would measure to see how far out it needs to be then pull the shaft and mark it where the lower half slides into the upper half. Next place a
flat washer over the threaded end of the shaft and thread the nut on until the threads are flush with the top of the the nut. Next clamp the lower section in a vise and use a open end wrench behind the washer and hit it with a hammer until the required length
is between the mark and the end of the upper shaft.
There are other ways to get it done I'm sure you can do it.