Originally Posted by Sea Aych
^^ might be the u-joints. Doesn't make much vibration at all, just a droning noise. i'll check for play tomorrow!
if you separated the two halves as mentioned you throw the balance of the shaft off. that is why they need to be marked before taking apart. Balancing will run about 200.00 usually includes fresh joints and center bearing.
squirt some rust penetrating oil into the joint to loosen up the needle bearings. something you should keep on to make sure they don't seize up. start there and see what happens.