I've read many posts on this already, but here's my story. Recently bought a used FX4 SCREW, I put in 4WD for the 1st time and once I got to the top of the grass hill I was on pavement. Switched back to 2WD, went back to the gas and HUGE THUMP, and then grinding at the passenger front wheel. So from reading these posts I've replace the solenoid. Grinding is still there until I engaged in 4WD and it goes away. But when I switch back to 2WD it makes no sound for 3-4 mins and the grinding starts again. Does this sound like I have a vacuum leak somewhere or is this the same result given when an actuator goes bad?

Thanks for any help

 

I just posted a nice thread for this. It seems that you need to bleed the 4x4 lines from air/water or replace the actual lines.