It started this winter, Once or twice all winter. On a snowy day, I locked my 04 FX4 into 4x4... It would allow a little wheel spin then the 4x4 would ''hook'' or snap on. Then it was ok...Almost like it needed to align or something. Then it did it again a couple of weeks later...And it even did it about 100 yrd further down the road when I was more aggressive on the throttle(thinking it was fully engage). I was a little concern, but reading that a lot of people were experiencing the same little clunk when engaging the 4x4, so I figured it was normal.

Then last weekend, I got stuck on ice on 2x4. So, from a Dead stop I put the 4x4 on and gave it a lot of time to engage and was very light on the throttle because I was afraid it would spin the rear wheels and then slap the 4x4 on. The rear wheels were spinning and the The 4x4 wouldn't engage and then a grinding noise came from the hub, like it was spinning the shaft, but it wouldn't align with the gears in the hub. I put it in neutral, and then reverse...and it did locked up.

So now I'm really concern with the 4x4, so I get out with the 4x4 on and drive it a little ways down the road (still on 4x4.) And it seems like every 3 or 4 revolution of the tire, something snaps and it sounds like its coming from the hub...
on 2x4, everything is quiet and ok. What's my problem?

Do you think its the hub or the shaft(stub)? If so, what needs to be replaced?

I appreciate the help guys!!!

 

i have the same exact problem on my 2005 f 150 4.6 and I am about to take it to ford becuase now it want do nothing at all just grind in the right fron hub

 

Search IWE Solenoid. im not 04+ savvy but i think this may be what your issue is.

 

Its fixed. It was a vacuum problem inside the hub. There was a tiny hole which was hurting the vacuum's performance. (it was taking 1 second or 2 to engage the hub into the 4x4 position.)

Replacement cost was 135$.
No more clunk when I lock the 4x4. So now mine locks instantly.