I know that this is a constant problem and I have read many suggestions on what to do about it. While in 2wd my hubs are trying to lock in. I followed what someone on this site suggested and pulled a vacuum on the system and everything seemed good but my question is if I pull the vacuum hose off of the solenoid that goes to the iwe's should I read vacuum at the solenoid. I know I've got between 16-18 pounds going to the solenoid from the intake but nothing is going to the actuators. I've replaced the check valve and the solenoid twice thinking maybe I got a bad part. It's driving me crazy. This is the newest and nicest thing I've ever owned and want it fixed.

 

There is a whole sticky thread on this topic here.

 

I've read the sticky but couldn't find a answer addressing my question about the solenoid

 

In 2wd you should get vacuum at the hubs then follow that to the output side of the solenoid and there should be vacuum there too.

 

I'm not getting vacuum down to the hubs. Pulled the line off the solenoid that goes to the actuators and not getting vacuum going through the solenoid. Have replaced it twice

 

Is there power going to the solenoid to activate it?
If not, why not? Fuse? Bad wiring (squirrels!!)?

 

The front hubs must have vacuum to keep them from trying to engage.
If you have none going to the lines with the motor running, that's the first issue.
I know it sounds backwards but that is the way the system is designed to work..

 

Bluegrass7, I wasn't sure if you meant to quote me or not but here is what I understand:

He has vacuum going to the solenoid but no vacuum after it. He has replaced the solenoid twice with the same outcome. That's why I was asking if there was power at the solenoid to (de)activate it. If not it could be stuck in the closed position.

 

In 2wd, you won't always have vacuum to the IWEs. Your truck has a warmup strategy for the front axle when first started, and
with every key cycle, regardless of the ambient temp. Once you drive approximately .5 mile, the solenoid will energize, and allow vacuum to the IWEs.
Suggest you start and drive it around the block, DO NOT shut off, and check the vacuum again.
Do you have a 4A TC? Can't tell what trim level you have.

 

I'm not so sure about that warm up.
I could not get my drive way plowed from the last multiple snows over several days time and needed to use 4wd in wet/snow mode to get out and in for several weeks.
The front lock up comes up on the dash screen, is delayed about 5 to 8 seconds to engagement and it's ready to go. Same delay when going back to 2wd.
The transfer case has to operate and the front lock up. These take a few seconds to work, it's not instant either way.
Never noticed a long delay for these to operate from a cold start.
When I get to the road and go back to 2h, it takes the same delay time to switch out the transfer case and the front lock or I cannot make the turn onto the road with the front locked up without hard steering and slipping the front tires on the road surface.
Rear lockup should not be used in the Wet/Snow selector mode for max traction because the ABS system takes control of all 4 wheels for slipping minimization.
Works like you can't believe.
Truck is 2018 5L XLT SCREW
Other levels and builds may do things differently.
This one is the best 4wd I have ever saw and hardly ever need to lock the rear up for snow use. It auto 'unlocks' past 25 mph anyways so only good for or near crawling speeds in 4hH. 4L is quite a different operation.

 

2019 F-150 - 4WD - Revised IWE Operation Strategy After Initial Start ***SSM 48088***SSM 48088 - 2019 F-150/Expedition/Navigator - 4WD - Revised IWE Operation Strategy After Initial Start Up

2019 F-150/Expedition/Navigator vehicles equipped with four-wheel drive (4WD) have a revised transfer case control module (TCCM) strategy that will affect integrated wheel end (IWE) operation after initial start up. The TCCM will not energize the solenoid to supply vacuum to the IWEs after the initial key cycle and a driven gear is selected. The IWEs will remain engaged for 0.8 km (0.5 mi) when the temperature is above 0°C (32°F) and 3 km (2 mi) when below 0°C (32°F). The strategy changes were implemented to improve vacuum supply management and axle warm up in cold temperatures. The engine must run for a minimum of 5 minutes to build sufficient vacuum before performing any vacuum related testing. Refer to the Workshop Manual (WSM) Section, 307-08A - Four-Wheel Drive Systems - System Operation and Component Description for additional information

There's another one out there as well, covering previous years. My '17 had this"feature".

 

Did you mean: TECHNICAL SERVICE BULLETIN 4WD - Intermittent Grinding Noise While Driving 20-201317 January 2020TECHNICAL SERVICE BULLETIN 4WD - Intermittent Grinding ...
www.f150forum.com › attachments › 559578d160164...
PDF

Follow this link for the other TSB

 

Are @RoundsLu#816 and @Bluegrass 7 the same person or did we lose the original poster RuondsLu#816 already?
BlueGrass7 has tons of posts so I wouldn't think they're the same person.

 

No, don't think so, but don't listen to me.

 

Wonder if the OP got things done?