I found a solution to my 4x4 problem where the front tires were not getting any power. Hopefully this may help someone else in the future. I checked the following in 4WD: The front driveshaft was turning, the vacuum motor was pulling the actuator rod in, the rod is spinning the shaft that enters the top of the Diff so the roll pin was good. The problem was the front wheels did not get any power. One other symptom was when engaging 4WD when moving there was a sound like a sprag was not engaging.

Enough background, The problem was there are 2 vacuum control solenoids on the firewall behind the battery, 1 controls 4x2 disengagement of the front diff and the other controls 4x4 engagement. The 4x2 solenoid was never closing fully so that the vacuum motor had vacuum on both sides of the diaphram which would not allow the actuator rod to fully recess. $33+1 minute to replace solenoid = FourWheelDrive again.

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1997 F150 4.6L 5speed SC 4x4