ok so my 4x4 shifts in you can hear it fine but when i get under a load if feels like it pops out and it sounds really bad like mettle grinding on mettle but if i let off of the gas for a bit its fine again. what could y'all think it is. my thoughts is the lines are bad and leak so under load they make it do that or i have a bad hub? its a 2006 fx4 5.4 it does it in 4low and 4high

Will

 

https://www.f150online.com/forums/ar...then-some.html

 

thanks man! i have read that before looks like I'm going to get a vacuum pump.