Variable Effort Steering Sensor

1998 GMC K1500 SLT Z71 4x4. Approx 66,000 miles. Auto trans, 350 V8.
Symptom: When making lane changes at normal street or highway speeds (30 to 70 MPH) steering will sometimes feel "loose" because the power steering assist suddenly reaches a level that would normally be applied when turning the steering wheel at low speeds or when standing still. This symptom is most prevalent when temperature are around or below freezing. Symptom first exhibited last winter when mileage was around 59,000 miles. For several years prior to this I would notice a "gronking" sound when making low speed turns, like surfaces of two materials chafing against each other. This noise used to be heard only in winter months: now I hear it almost all the time. I don't know if the "gronking noise is related to the steering sensor problem.

Question: Can the steering sensor be serviced or should it be replaced? Either way, how do I remove and reinstall the sensor? Any comments on the "gronking: noise problem?

Thanks for any info provided.

Gary - Lockport, Manitoba, Canada

And yes, it is snowing today-it is currently a warm 26 degrees fahrenheit