i just put a 6 " trailmaster lift in my 07 150 whenever i put the truck into 2 wd the front drivers side hubd makes a grinding noise , but when its in 4wd its silent. so i took it apart and the part that engages and disanges the 4wd was cracked and whenever i got on the truck in 2wd it started to try to go into 4wd thats why i heard he grinding i got the new part but im wondering if i should replace the spindle also

 

I had the same thing, there is valve that engauges the hubs with vaccum.the valve could be bad allowing the vaccum to 'leak' through the valve and slowly try to engauge to front hub.Had two go bad on my 04 scab fx4. The valve is on the passenger firwall in the corner right under where the wiper cowl drains all the rain water right unto it.I fabed a shield out of some flashing and no probs since hope this helps!