tiresmoke19

my sister just bought a 98 f-150 and now the 4x4 dosn't work the front driveshaft spins but dosn't turn the wheels any help ?
i've heard those are vacume operated?

wwb

The truck probably has the "automatic" hubs if it has a dash-mounted switch for 4WD. There should be 2 positions on the front hubs, marked "auto" and "locked" or something similar.

The purpose of the hubs is to connect the axle shaft to the wheel when in 4WD and disconnect them when in 2WD. They are actuated by vacuum, but can be locked manually if the vacuum system fails.

If the 4WD is engaged by pulling a lever down on the floor, then the truck has manual hubs, marked "free" and "lock" or something similar. These must be locked or unlocked manually.

tiresmoke19

this truck has the manual on floor shift trasfercase but no hubs to turn like the 96 and older fords i think the axle shafts always spin and somehow lock togather in the diff when turned on ???????????????
any ideas

Thunder1

Just had this happen to my 03. More than likely it is the shifting fork in the front diff that worn out. It's a cheaply made aluminum fork. Mine wore out after only 60K. Maybe around 100 miles a year in 4WD.

lubomir

I had the same problem with my 97 F150. The shifting fork in the front differential was not moving. Removed the small cover, sprayed it with WD40, moved it back and fort with a screw driver as I engage/disengage 4WD. I did this until it was moving freely. I have to do this once a year to keep it working.