1999 ford f150 ,4x4 wont engage
stick or push button 4x4
bad acuaitor,or motor on back of transfer case.or striped splines on front axle.
if you have the turn button 4x4 it's highly likely that you should check out the vacuum lines for the 4x4 are still connected and aren't cracked or anything, i've seen that several times.
what do the 4x4 lites do on the dash? if its esof(electronic shift on the fly, its more than likely the shift motor or the actuator and fork to engage the frt end, you will have to retrieve codes from the 4x4 module to know which one, if its msof( manual shift on the fly) its probably the actuator in the frt.
i had a problem with 4x4 not working , it was a vaccume line behind battery . got knocked loose when installing new battery,
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