humming noise in 2Hi that goes away in 4Hi is typically IWEs.

 

Go to youtube and search "f150 iwe noise"
Is that the noise you are talking about?

I just went through it and had to replace the front left IWE actuator. It would make noise in 2wd but as soon as I switched to 4A or 4x4 it would go away, and then come back immediately when I switched it back to 2wd.

 

Yup. If you pulled the axle out and didn't re install the IWE actuator to the axle with vacuum before reinstalling into the hub then there's a possibly it will need to be replaced.

You can pull the axle and actuator back out to inspect it. Takes all of 10 minutes. Get your self a cheap vacuum pump so you can check the actuator.

I messed up and didnt install my axles back in properly and destroyed the driver's side which caused a vacuum leak which eventually destroyed the passanger side.

The passenger side still held vacuum but the collar that engages and disengages the hub is riding on plastic that broke.