2006 Ford F-150 - 4WD system issue

2006 F-150, 107,000 miles, used as second vehicle,pulling aluminum fishing boat. Recently driving up icy hill, I engaged 4WD. Front wheels did not engage. After getting out of predicament, returning on flat roadway, 4WD engaged. Possible malfunctions/diagnosis I should pursue? Thanks. Dave Johnson, St. Peter, MN

Are you sure it did not engage? The front wheels will just spin on ice just like the back wheels. 4wd does very little on ice, if anything.

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Ask shop to put vehicle on lift & test if the 4WD engages the transfer case. If so, it would cause the front axle shafts to rotate. If the shafts aren’t rotating, problem is related to transfer case. If shafts rotate, problem is the front hub-locking mechanism. Not sure how the hubs lock on your truck, some 4WD vehicles of that era used vacuum actuators, hose leaks and prevents vacuum from reaching necessary level to lock the hubs.

We’ve had some prior posts here about 4WD hub locking problems. Use the forum search feature, upper right this page.

If hubs seem to lock ok except in certain situations, like cold, icy temperatures, ask shop if cleaning and re-lubing the hubs might help. I replaced the front brake parts on my Ford 4WD truck recently, and cleaned and re-lubed the hubs as part of the job. Definitely easier to engage now.

OP’s ford 4WD is activated by vacuum. if there was a vacuum leak the hubs would try to engage and you would hear grinding, even in 2WD, ford trucks of that era had problems with water running onto the 4WD solenoid and cause it to fail. in the picture below the one on the left is the original. the right one is the updated version with a cover. the 2WD solenoid is missing in the pictures.


Only if you want to get the problem fixed.

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It won’t engage if you were trying to engage 4WD while the rear wheels were spinning.