I have a 2003 F150 with shift on the fly 4x4. When i put it into 4x4 it clicks and the light comes on but the front end does not lock in. I looked at the accuator on the front axle and it moved a little bit but when tried it again it did not move anymore. Can anybody give me a clue what i should try out to fix it

 

Check to make sure you have vacuum or enough vacuum going to the actuator.

 

ok how exactly do you go about checking the vacuum. How much vacuum is there supposed to be there?

 

Read this post, kinda bounces around between 97-03 info and 04 up but should help you out.

https://www.f150online.com/forums/ot...4-problem.html