Drive lines generally have a zerk fitting for adding grease. There are some that are sealed and never need grease added.

There is another culprit which will cause that sound -- u-joints. Not all u-joints have a zerk fitting.

You need to crawl under and physically check for the presence of a zerk fitting on your drive shafts. If you have a fitting, add grease.

While you are at it, check your u-joints for zerk fittings.

Sometimes you can visually spot a bad u-joint due to rust and powder around the caps. However, grabbing the driveline and twisting is another way to check for play in u-joints.