04 f150 xlt 5.4L

first post. Love this site.

I have a strong vibration in the front end only when I engage 4hi or 4lo. I've grabbed and shook everything under there and nothing is loose (sway bar link was ripped out of a bushing but that was an easy fix). front dif and tcase fluid is full. Front drive shaft spins not even a quarter turn (I was told that was normal) when turned off. I'm stumped and tryin not to take it to a shop. Any ideas would be helpful thanks.

 

Bent front driveshaft or a bad ujoint?

 

Driveshaft is fine. I thought it was Ujoints but my buddy said they are fine. I bought new ones anyways and while takin the drive shaft off I can hear it turning in the front diff and wasn't sure if I pry it too hard if it'd break something in there?

 

finally got it into the shop. They came out with a oil pan that was just straight milk from the front diff. When I finger tested it bout a month ago it was fine. Might go double check it but seeing as I live in Alaska and it doesn't fit in a garage, I don't really want too haha. My question is if its already vibrating am I just gonna have to replace the front diff or could a swap of fluid fix it? I know I won't know for sure till I take it off but I just wanna hear some opinions cuase when it comes to gears and all that I cringe so I'd probably have the shop do it but I just don't wanna spend 2500 right now. any thoughts would be awesome thank you.