I have a 2011 F150 FX2 with 5.4 V8 and electric steering. A couple of years ago the steering became sticky and progressed over time. In order to turn in either direction force was needed to overcome resistance from nearly any position and did not return to center on its own. Recently I replaced the intermediate steering shaft (which had corrosion on the shaft causing resistance over rough areas) and the coolant reservoir hose which would leak on cold days. I suspect the coolant was the culprit of the corrosion. This improved steering a lot but there is still resistance when turning left of center and returning to center. Alignment was checked out to be good by two places. Dealership says I need to replace rack and pinion. Is there any other possible culprit? Thank you!