word to the wise
if you are taking a steering rack and pinion out take the pinch bolt in the steering knuckle all the way out because it is not a real pinch bolt itt is a bolt in a keyway valley and you do not want to take the steering knuckle all the way out it is the pits to line back up
You must mean the steering shaft coupler. Yes virginia, the steering system is unusual at many points of assembly. This is because the parts must fit exactly so harry homeowner does not unwittingly substitute incorrect fit or substandard pieces. The parts must have thew specified range of motion and tensile strength. The steering knuckle you mentioned is the part that connects the lower control arm and the strut. it is steered by the connection of the steering linkage. Many applications, it can be the part that supports the hub and allows the front drive axle to pass through. The taper fit there at the steering linkage is also specific to make model and year. For help lining up the steering coupler at the steering gear input shaft, the pinch at the coupler clamp can be widened some with a cape chisel. This can be done during disassembly. Careful observation may indicate a factory v groove on some with a master spline while others have a round and 2 flats. Happy rack. Hope this helps.
(The, not thew), and a steering knuckle also supports the brake caliper. Cars that have tapered roller wheel bearngs call the steering knuckle the spindle for obvious reasons.