Also spin the tires on a jack and see if they have a hop or the tread wiggles. You could have a bad tire.
A drive shaft vib will be all the time, a tire will be at its worse at about 45 mph.
edit,
I will get a battery today to put in my camera, I will try and cover everything from the axle to the t-case...I will be putting in a spare 3rd so while I am at it I will take pics of the extended driveshaft and also of the gears (because I know they are completely gone).
You can't shouldn't extend a shaft without replacing the whole tube and it must be true.
