Would like advice from someone who has experienced this.

I am experiencing difficulty with engaging the 4 x 4 on this truck.

I have an F150 4x4...2001, with the electric transfer case shift moter and dash mounted selector switch. This is what I have observed so far, and what I have checked.

The truck will go into 4x4 hi mode occasionally if I switch when stopped and 'ease' forward slowly. But then it will drop back out again after a brief period of time.

It never seems to engage the 4x4 in low range, although the transfer case will shift into low.

The vacuum 'motor' located on the front axle is clean and free of obstructions and seems to work. I have observed it moving in and out when using the dash switch.

I have supported the vehicle with jackstands on all corners and observed that when the unit did occasionally engage the 4 x 4 drive, the front drive shaft rotated. During all other events it would not. By that, I mean not engage during most instances of selecting 4 high...never in 4 low and not after it seemed to 'drop out' of being in 4 high for a bit.

So if the front axle vacuum 'motor' is working, and the transfer case electric shift motor is operating such that it will drive the transfer case into each of its 3 ranges....2 high, 4 high and 4 low, what else is preventing the 4 x 4 from working properly?

 

It sounds as if the motor in the transfer case is not working properly to engage the front driveshaft.

 

Thanks Lxman....

Perhaps the electric shift motor can move the transfer case through each of its ranges and still not communicate properly with the 'gem'....I understand that I have a solenoid controlled clutch of some sort in the transfer case to aid the synchronization of the gears while the truck is in motion...am suspecting an electrical failure in this, or with a contact or component, relating to this....My Haynes manual is woefully inadequate in this area.