something getting loose in the drivetrain

[the missing link]

Yes the international were horribly for the damm u- bolts backing off , most of the time you can see them working back and forth .
You should be able to pull the plug and look at it , being a magnet plug .
And I have never done a front diff in the bush , using just my quad whinch ,lol
One trick is to get some threaded rod the same size as the bolts , use it as a guide to line everything up and to pull the diff into the housing . It may not be right be works real well .