when i am driving theres no problem but when i switch the 4x4 on it pulls to the right and it starts to hum and vibrate from the pass side front.it wont stop until i stop after turning off the 4x4.
i put it up on jack stands and it does not hum!!!
is it the hub?
4x4?
please help me!!!!!!!!!!!!!!!!!!

 

Hey im not sure what the noise is. Im interested just incase mine does it one day but what year and model do you have

 

only does it in 4wd? what year truck ? the more we know on the forum, the more we can all help you out!

 

2000 150 lariat 4x4 auto ,electric 4x4, 5.4 106000mi

 

are the tires on the front end the same diameter? It sounds like a silly question, but sometimes even the same 'size' tires can be different enough, especially if the treadwear or the manufacturer is not the same.

Aside from that, maybe an axle engagement issue?

 

same size and tread ware