2010 F150XLT so there has always been this noise probabaly for about. Year now, thought it was just a suspension issue. Well I want to gone. So I changed both hub assemblies, control arms and struts. Noise is still
there. so I read that 4WD actuators go and engage some times and make a grinding noise. So i had those replaced the noise was gone until about a mile down the road. So I thought it was the check valve which ppl say go bad. Changed its noise is still there. So I changed the 4WD valve/solenoid and the noise is still there what next change out all the vacuum lines to the actuators or what?? It’s a grinding noise and the RPMs seem to twitch when it grinds.

You don’t say where the noise is coming from. Based on the fact that it changes with the rpms, might be the rear pinion gear.

it can’t be the rear the sound coming from the front I feel like it’s the front driver side more so but could be the middle??