5th Gear drumming noise?

hi there..
right iv just bought another defender, 200tdi this time, 1993.. still running her in and tuning myself to her uniqueness..
Now iv noticed when in 5th gear she drums alittle; now i know sitting in a tin ontop of a lot of revolving mechanisms underneath (its gonna drum) but when you get to about 35-37mph it gets a hell lot louder.. then at 40mph it disappears.. now my first reaction was i think that difs going? but is that me being over causcious and looking back to my old freelander dif troubles or am i onto something? or is it just at that point where the whole vibration is just perfect to create that noise??

Can anyone help me out here, or give me a few pointers as what to look for?
thanks alot guys.

Prop Uj',s? probably related to your other post.

Either check for play in em ignore the problem or keep above 40mph

UJs are sorted now.. deffinitly not them.. drummings getting louder tbh.. just waiting for that dreaded bang! and just before the snow ey!

at least you will know whats wrong then!