All,
Ive replaced both actuators, all of the vacuum hose, the solenoid and the check valve in my 2018 3.5 xlt. Still grinding…. Any ideas? Can the truck not produce enough vacuum to keep the actuators not partially engaged?

 

Forgot to add, the grinding goes away when put into 4wd, and when I shut the truck off and poo the hood there is vacuum in the reservoir

 

Buy a vacuum gauge set from Harbor Freight and post real numbers rather than what you think it is doing.

 

vacuum pulled from main line in front of check valve or 20 in at idle and 24in at 2000rpm. When I put the vacuum gauge on the solenoid it pulls the same amount of vacuum as the line in front of the check valve. Disconnecting the main vacuum line from the solenoid the line holds 24in. Vacuum reservoir pumped up to 20in and holds steady.

 

Put the vacuum guage right at the larger hose fitting on the metal tube going to the IWE, see if full vacuum is there on each side, jack the front off the ground so you can spin the wheels and see if there is noise when you go to 2whd. If you have an early 2018 manuf. the TCCM transmission control module needs an update so the solenoid does not send vacuum to the IWEs untily the truck drives 1/2 mile to give the canister time to build up a good amount of vacuum. Also each IWE has a vacuum line, and a vent line, if the vent line the smaller one is clogged usually by frozen humidity in cold weather the IWE holds vacuum but does not move because the vent is blocked. Also the IWE diaphram can be coming loose from the IWE ring gear. The IWE can be over greased and cold weather makes movement of too much grease sluggish. Or the IWE and the hubs can have their teeth ground off by too many times of making the grinding noise without being repaired. Ane Per Ford TSB any truck of this vintage that has the 4A selector they can not repair and Ford just caps off the vent lines and keeps them locked to the hubs full time. On newer F150s with 4A Ford never bothered to install IWEs at all and just spins the axels.

 

also checked the vacuum the Iwe was receiving by hooking the vacuum gauge to the supply hose and it’s 20in at idle, both of the Iwe hold a steady 25in

 

just took the truck out and drove it, it’s 2 degrees out. Had Iwe grinding as usual. Drove about 20 miles, wanted to check and see if I had any leaks when things cooled down. Pulled the hose off the driver side iwe and still had 20in at idle.

 

also my truck does not have 4a, does pulling the power to the solenoid and just leaving the hubs in gauged hurt anything?

 

I'm a little confused here, early morning or olde age, don't know which. Anyway, here's the TSB from Ford showing how things are done at the dealer.
https://static.nhtsa.gov/odi/tsbs/20...71859-0001.pdf

 

Thanks for the replies, I think something else might be going on. I parked to truck outside for a few hours to check all the vacuum lines and Iwe when they were cold (-2 outside). I pulled the line from the driver side actuator and had zero vacuum. Checked the solenoid at it wasn’t opening to allow vacuum to the system. Shut the truck off and after it warmed up in the garage I started it again and had instant vacuum past the solenoid. Any ideas?