03 F150 4.6 4x4 auto Ext/Cab Shortbox

Vibration above 50 mph, and notice steering on hard turns (slow speed).

4x4 engages and light comes on, and then turns off based on dash selector

Vacuum to both solenoids. No vacuum past either no matter the selector position

Neither solenoid click switching from 2WD to 4WD

Power to both solenoids ~13 V no matter in 2W or 4WD

Fuse 23 and 104 (PDB) ok.

Not sure how to troubleshoot GEM or Transmission range selector?

Help appreciated.

 

The solenoids will always have power present.
The Transfer case motor 'position' supplies the grounds to operate either one as needed.
Sounds like the solenoid for release is stuck.
One pulls the vacuum device at the front axle in to lock the right front axle halves together.
The other solenoid pull the device to unlock that axle.
There are no active front hubs on these trucks..
If the dash light comes on and off with the dash switch action, it tells you the case motor and wiring is good and nothing wrong with the GEM.
The release solenoid valve is stuck.
If you go for replacement, get the right one because they made a change and the new design won't fit.
Good luck.

 

Ok, so after disconnecting vacuum lines and electrical lines around solenoids, and removing and reinstalling both fuses, and in between switching 4x4 on and off, it felt like the hubs unlocked.

I thought I was ok with some bad connection.

Wrong, now 4x4 won't engage. Light comes on, but nothing.

If I replace the release solenoid, I believe it's the inside one with the pink vacuum line according to diagrams I've seen posted.

RockAuto shows only the Actuator (AIRTEX/WELLS 1S12513). Is this the same as the disconnect/disengage?

I believe the Disengage Actuator is supposed to allow vacuum when 2WD is selected.

Thanks

 

Either side is the same but the actual part can be either the 1S12513 or 600400.
The plug up connector is different between them.
Notice one is slightly rounded, one is rectangular.
The rectangular type is the older design.
.
The internal piston valve can stick in its bore and only very lightly spring loaded.
Under the top cap is a vey small filter. It can go hard and crumble getting into the vertical bore.
Under the front Axle behind the black cover is the front actuator.
3 bolts holds the cover on.
Use a vacuum pump at the lines from the firewall and see if the actuator moves both ways.
Manually move the arm to see if it is too stiff to move under vacuum actuation. It checks the lines and the actuator.
If you don't check it all out it can dog you later on.
.
What is done to lock 'one' axle is a sleeve is moved internal that locks /unlocks the axle halves.
That's all that happens.
Obviously at this point none of this action is electrical so the dash light can falsely indicate the front is locked/unlocked.
Good luck.

 

Thx for comments so far.

So I found both solenoids had no resistance, so replaced with a used assembly (both had ~73 ohm).

I also cleaned up the actuator connections to front differential and attempted to lube, but didn't manually move.

I checked solenoid operation were correct:
- 2WD (inner with pink line) only opened vacuum when in 2W,
- 4WD (outer with green line) only opened vacuum when in 4W.
Problem almost solved.

Front free in 2WD highway (no vibration) and 4WD engages (mostly).

It may be as simple as a vacuum leak (maybe at solenoid where I’ve been disconnecting/reconnecting), but 4WD seems to slip once in a while in front (clunk).

I haven’t had access to a helper, so maybe I’ll try recording action with my cell and see how the engagement is working.

More to come.

 

Latest Update - Front Not Engaging At All Again.

As noted previously, the Front was partially engaging, and I found after switching 4x4 on off on, by the second time the front fully engaged. That worked for a while, but not any longer.

So I double checked the fuses and solenoids working fine. I checked the vacuum to be ~18 " on both lines to solenoids.

I viewed the engagement arm moving to drivers side in 2wd, but the arm barely moved right (passenger side) when 4wd attempted.

So used vacuum guage at lines from solenoids, 2wd (pink) held vacuum, 4wd (green) line did not. Disconnected Green at Actuator end and line held vacuum. I assume this means the actuator 4x4 diaphragm side has a leak.

So off to wrecking yard to find an actuator.