Drivetrain 'Squeak' when backing up

[Coley]

Hi guys.
I'm a fairly new member here but I must say there is a lot of good info and well informed people here so maybe some of you could help me out.
I have a '72 1/2 ton with a 350, 2 piece driveshaft and a stock 12 bolt (open) rear end.
I've been picking up on a couple of things lately. First is a cyclic or rotational 'squeaking' in the drivetrain when I'm backing up in reverse....this condition is about 2 months old. Second, "ve been starting to notice a little drivetrain vibration at/above 40mph.
So,....do you think this is U-joints, the hanger bearing....or something else?
Any experience with something similar to this?
Many thanks in advance guys, I appreciate the feedback.
Coley