I into (I hope) the end of troubleshooting my '97 F150 ESOF lack of 4X4 problem.

Transfer case is shifting into 4H and 4L but front axle is not shifting into 4WD.

Vacuum solenoids on firewall have vacuum on the supply (black line) side but no vacuum on the pink or blue (output) side.

I also have no way to supply a vacuum to the axle shift motor to ensure it is functional, but my feeling is to deal with the lack of vacuum at the solenoid outputs first and then the shift motor eventually if need be.

Seems like the solenoids are a dealer item with the exception of an occainsional loisting on eBay, but the axle shift motor seems to have a bit of aftermarket availability.

Any words to the unwise about my troubleshooting as well as using aftermarket parts to resolve this ?

Thanks a ton for all the forum help, it's very much appreciated.

Pyzon

 

The disengage solenoid vents to atmosphere when the GEM commands engagement of the front axle lock up. So you should not see vacuum on that side when in 4x4. You may have a defective engage solenoid.

Regards

Jean Marc Chartier