S10 Power Steering Box Question

[BRDog509]

The 1995 S10 power steering box I am using has an input shaft as shown in the attached photo with a smaller shaft protruding through the splined outer portion and a pin going through both parts. The smaller shaft is broken off even with the pin that goes through the shaft. My question is what is the purpose of the inner shaft and is the splined outer portion depending on this pin to hold everything in place? I have been unable to find an exploded diagram of the steering box that shows this detail.