Had my truck into the shop for an oil change and some other small things. Told my friend that is the mechanic about a grind that has happened a few times. In the mornings, cold frosty mornings. There was a "what sounded like to me" a gear on gear grind. Right away he said he knew what it was. There is a vacuum solenoid on the firewall that goes bad quite often in the f150's. He said what happens is that the 4x4 will try and engage but the gears will just sit there and rub. The part is really cheap and he will install it next Thurs. So if you hear this sound, check the small vacuum solenoid behind the batt on the firewall.

 

so did this end up fixxing the problem cause im having the same trouble that had but i wouldnt say its just on cold days i traced my vac lines back to that selinod but wasnt really sure if that was what it was or what it did at the time but that was on my list of things that could be wrong

 

thats what it is i get that on my 95 when its real cold but i dont worry about it but its the transfer case trying to engage it in 4x4 that mechanic was right.

 

I read a post a while back apparently the solenoids on the passenger side of the firewall like to soak up water and stick. This leads to a strange grinding sound kind of like a stick stuck under the truck scraping the road. Ford has a replacement with a shield to prevent the water running off the cowl from getting in the solenoid. (once its wet you can't trust it.) I had this problem, replaced the part, no more problem.

 

I replaced that part with the new style.. Still have the grind.. I think it is the hubs.. anyone still have the issue with the new part?

 

right by that selenoid are 2 in line check valves that let the vac flow one way and not the other thats what was makin the noise on mine its easy to check ur self just pull them out of the lines and try to blow through them u shouild be able to blow one way and not the other if u can blow through both ways bingo thats ur problem

 

just went outside in the freekin 10 below temps.. lol.. Pulled the vac lines from the solenoid and tried to blow into them, could not move any air at all.

 

u need to pull the valves there is 2 of them one comes off the intake line and one comes off the selenoid there right in the line i think they r clear plastic on one side and black on the other side

 

just remeber what way they were in

 

here is a great link that will really help u understand how your 4 wheel drive system works and how to trouble shoot it
http://www.ford-trucks.com/forums/836438-everything-you-wanted-to-know-about-the-iwe-system-and-then-some.html