4WD not working while IWE engaged?

JOSH FX400

MEMBER
2005 FORD F-150
5.4L
V8
4WD
AUTOMATIC
130,000 MILES

I have been doing a diagnosis on the 4wd of my 2005 ford f-150 fx4, when putting it in 4 high can hear a little click but there is no change, same for 4 low. I jacked up the front of the truck to find the IWE’s were engaged and there was no vacuum to either side. I then took off the connections to the IWE Solenoid and connected them together and for the first time since I have owned the truck the IWE disengaged having the wheels turn freely of the axle. So, my questions are #1 what could be my problem not getting constant vacuum my IWE’s while in 2wd and #2 since my IWE’s have been engaged all this time why hasn’t the truck been in 4wd? And what might be broken?

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,924 POSTS

The IWE in 4wd with not have vacuum at the actuators, FYI. I found this

Operation: In 2WD mode, vacuum pressure is applied to the IWE actuators, disengaging the front wheel hubs from the half-shafts, effectively keeping the vehicle in two-wheel drive. When 4WD is engaged, the IWE solenoid reduces the vacuum pressure, allowing spring-loaded mechanisms in the IWE actuators to engage the front wheel hubs with the half-shafts, thus providing power to the front wheels.

To me it sounds like the transfer case mode actuator is not working, here is the location so you can remove it and then work the controls to see if it moves to confirm the failure. Check out the images (below). Let us know how it goes.

Image (Click to make bigger)