I have an 06 F150 with 35K miles. I really don't drive it much. I went to get a load of wood today and heard a "rattling" noise when accelerating. The sound is similar to a loose converter shield. The strange thing is the noise quits when I put it in 4WD. I looked underneath and didn't see anything obvious. I'm thinking a dry u-joint. Any ideas?

 

Do a search in the 04-08 section for IWE.

 

Thanks for pointing me in the right direction. I just changed the IWE solenoid and it didn't help. I have to dig deeper. I bought the truck new in 06 and barely drive it. This is ridiculous...