I've got an 04 stx 4.6l 4x4. Yesterday day I put the truck in 4h and 4low just testing it out. Engages and disengages perfectly. I should also mention it's a hand lever not electronic. I have a slight buzzing sound coming from what seems like right underneath my feet at around 40-70 mph. Definitely a spinning metal to metal contact type sound. Hoping its not something in the t-case. I've read about 49 posts on here and found one that was rather similar to my problem but I know nothing about 4wd systems so I'm not sure if a hand lever 4wd even has a solenoid. I recently got rid of my 98 f150 that had the same problem but that was electronic 4wd and I replaced the solenoids and all was good after that. I the noise is dedinitly happening with the speed of the truck. Gets more high pitched the faster I go. However it seems that once I go for about 10 miles at highway speed it seems to go away. I am totally stumped. ANY HELP EXTREMELY APPRECIATED. Thanks guys

 

I believe with the 04 body style, you have this IWE solenoid and I've read a lot of people have had issues with them. Search it and see if it goes along with your issues.

 

That's a lot of what I was reading, a lot of guys talking about their IWE. Their problems sounded a lot more severe than mine. I don't want to rule anything out. I just have this suspicion that it's not fully disengaging. Not sure if Thats an IWE related issue so I do plan on looking into tht.

 

IWE seemed too common, especially around 06/07 there was a lot of threads back then. if miles are low I'd suspect that before your tcase, probably your front end slightly dragging not the 4x4 output continuing to spin.