I own a 2011 ford f150 that has started making a grinding sound on the right front passenger side only when accelerating in 2wd but when i put it into 4wd its gone. I have changed out the actuator, silonoid, check valve and have pressure tested both lines with drivers side having 15lbs and passenger side having 11lbs. No leaks in the lines but still have the noise. Both front cv shafts also spin when in 2wd drive. Shouldn't they only spin when in 4wd ? Also pressure tested both actuators with adequate test vacuum lbs they are getting and both spin freely but when hoses are hooked up cv shaft spins with them. I'm stumped on what to do next.

 

4x4 vacuum harness. Replace it..

 

Gotta ask, did you use a vacuum pump, or an air compressor to test?
Use a vacuum pump, readings are in inches/Hg, not psi/#.
I'd like to help, but right now I'm a bit confused by your terminology. I'll find a Ford TSB that might help, it's for a newer vehicle, but it all applies to yours as well.

 

Here ya go, Intermittent Grinding Noise From IWE ***TSB 18-2273*** - Ford F150 Forum - Community of Ford Truck Fans