To start off I have a 2004 f150 with about 69k, 4x4 of course.

Well I had the rattle when underload, replaced the IWE solenoid, that didn't fix it. I also changed the DS IWE actuator which is where the noise was coming from. That also did not fix the problem. When I replaced the IWE it looked like **** but the teeth all looked good. I am at wits end with this truck. This has been going on for awhile and I just lost my job so I can't afford to take it anywhere. Any other ideas? Thanks!

 

There are tons of threads on this. However, to try and help we will need more. I understand is not working, but was not working and what is? Does your 4x4 indicator light up when you switch in? Have you checked all the fuses and relays? Are you able to get any enagement period? Did you check the vaccum lines for holes? FYI, if you got a problem with one side usually the other is just as bad. Also double check the vac and vent lines at the IWE to make sure you did not reverse them (if reversed you would not be able to draw vaccum to engage as it would be on the wrong side.

 

The vac lines are not reserved but I do plan on going through them to double check for any leaks. 4x4 does work, the light does come on, when it goes in 4x4 the noise is gone but when it 2wd and giving it gas it makes the noise which is almost constant. I did check both side in the air and only the drivers side seemed to have the problem. Thanks!

 

one of the check valves were shot so I replaced it. Didnt fix anything, going to dig more

 

To properly check vacuume system you need to use a pump and guage and see if it holds vac. you can't properly check the system just by blowing ( if that's the method you used)