I have a 2005 f350 4x4
I have some 4x4 concerns...feels like its in 4wheel drive right now.All 4x4 lights work and are not on.

So...if the hubs are in the "AUTO" position can I spin the driveshaft by hand?
I would think that it would not be in 4x4 and should spin.
Mine does not...

 

If you're in 4wd with the front hubs in auto (assuming they work), the axles should not spin by hand. If you're in 2wd, with the front hubs in auto, the axles should spin.

If the front hubs are locked manually, you cannot spin the axles.

It sounds like you're auto hubs aren't disengaging. Check for a vacuum leak somewhere.

 

Dont know a whole lot about the system but i thought the vacuum only engaged the 4X4 and they disengaged by spring tension when in auto.

 

Negative. The hubs are both engaged and disengaged via vacuum. I assume the springs assist after the vacuum is applied. The vacuum system is usually the culprit when diagnosing problems in the 4x4 system.

 

No. When you switch to 4WD, the PVH (Pulse Vacuum Hublock) solenoid provides a short (10-20 seconds I think) full vacuum pulse that pulls the lock in. When you switch out of 4WD, there is a period where the hubs are left locked (a minute or two), then the PVH solenoid provides a partial short vacuum pulse that releases the hubs. Think like the click pen. One push to extend the tip, another one to release it.

If your hubs are auto-locking, it would seem like you don't have a vacuum leak. It appears they aren't auto-unlocking though. I would recommed you start with a good hub cleaning. The only parts involved are some seals and good instructions can be found here.

Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page

 

Should I start shopping for some warn hubs?

 

"Should I start shopping for some warn hubs? "

You can use the ESOF hubs like manuals. Just turn them to "Lock" and there you have it. On a manual hub there is "Free" and "Lock". On auto hubs you have "Auto" and "Lock". If you are in Lock in either system your hubs are "On".

Here some info I got from a site, maybe this one, somewhere to test the system and address repairs......

Hublock Vacuum System Leak Test

NOTE: This procedure requires the use of a calibrated vacuum gauge that is accurate to within a minimum of 0.1 in-Hg. It is recommended the Pressure Vacuum Module 105-R0099 or equivalent be used.

Make sure hublocks are in the AUTO position.
Lift and support the vehicle off the ground until the front tires can be spun freely. Refer to Section 100-02
NOTE: The engine is required to be at idle during the following steps to supply the vacuum required for the hublocks to engage and disengage.
Start the engine and allow to idle.
Turn the mode select switch (MSS) to the 2WD position and wait 15 seconds. If switching from 4X4 mode, wait an additional 45 seconds.
Disconnect the vacuum line at the right front knuckle and install a vacuum gauge on the line.
Disconnect the vacuum line at the left front knuckle and plug the line.
NOTE: Normal operation applies engagement vacuum for 45 seconds and then drops to 0 in-Hg.
Turn the MSS to 4X4 and observe the vacuum reading. The vacuum reading should remain at or above 10 in-Hg for 45 seconds.
NOTE: Normal operation applies regulated disengagement vacuum for 15 seconds and then drops to 0 in-Hg.
Turn the MSS to 2WD and observe the vacuum reading. The vacuum reading should remain between 5.8 and 7.3 in-Hg for 15 seconds.
Remove the vacuum gauge and connect the vacuum line at the right front knuckle. Turn the MSS to 4X4.
NOTE: The right front axle shaft and universal joint should turn.
Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint. Turn the MSS to 2WD.
NOTE: The right front axle shaft and universal joint should not turn.
Wait one minute then rotate the right front tire one revolution forward and one revolution backward while observing the right front axle shaft and universal joint.
Install the vacuum pump and gauge line on the knuckle and pump to 20 in-Hg. If the vacuum drop is not equal to 0.5 in-Hg in 30 seconds, Go To Pinpoint Test G for further diagnosis of the hublock system.
Repeat steps 1 through 13 for the LH hublock. If results are not as indicated, Go To Pinpoint Test G for further diagnosis of the hublock system.
PinPoint G is going into electrical tests. I don't think you need that info for the problem you are experiencing.