Have a 2002 ford f150 4x4 manual transfer case i have checked the vacum to the selinoids on the fire wall have good vacum to them also have power to them constant no vacum leaving selinoids to front end to engage hubs is there a switch to activate selinoids or are they just bad? can put manual vacum on front end and it will engage hubs.
The vacuum shift solenoids have power to one side of them at all times.
The GEM applies ground to them, to activate them, after the shift on the fly position confirm from the trans case.
The power to both should be on the White w/ Light Blue stripe wire.
Ground to them ( from the GEM ) is
2WD : Gray w/ Black stripe wire
4WD : Red.
The only TSB I know of is for the 04-06 MY trucks, for the IWE solenoids ( the kind without the water shield ).
Did you jack up the front end ( and support correctly ) turn the key to the run position ( do not start ), and shift into 4WD, and check the front drive shaft ?
If the shaft still turns, the problem is in the transfer case, if not you are looking in the correct place.
The GEM will not signal a vacuum solenoid until the transfer case has shifted into 4L or 4H ( 4 switches that are the return signal to the GEM ). Could be a problem with the connector on the transfer case ( think it is a 8 or 10 pin connector ) to the contact plate position switches in the trans case.
There is a manual front ale cable, but I would think you would want to confirm why the GEM is not signalling the shift solenoids, prior to replacing them
Posilock make a kit for the F-150
Hello.
If you have vacuum to the switches and you want to check if they are operating, pull the vacuum harness off, twist it to one side and just put the vacuum side back on to the solenoid. Then feel the open side of the solenoid to see if vacuum is coming through the switches when you apply your 4 wheel drive.
One should allow vacuum in 2wd and then the other in 4x4.
There is a service bulletin on these solenoids as water intrusion is an issue. New new solenoids have a plastic hood to keep water from getting in them.
And if water has gotten in if you live in an area where the lines with water freezes it doesn't allow vacuum to your front axle actuator.
And of course you could have broken vacuum lines down to the actuator on your front differential.
Hope this leads you to a repair on your truck.
If you have any more questions leave a message for me in comments and I will check back.
KL
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hi and lo light flashed 6 times but the transfer case wont kick in.. they put a new moter and switch in it.. all the fuses look to be good..
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