I have a 7800 rear hub, the one that is 10 speed only. Got it on Craigs and it looked barely ridden. Almost as new as a take off.
It makes a tick sound when riding. I only know 105 and Ultegra rear hubs so far and my 105 hub will also make a similar sound. I am guessing it is a normal sound.

I know the wheel could have been sitting in a box for 5 years.
Is this normal for the hub or is there something wrong here? Thanks.

Ever use a ratchet? Same thing.

pedaling or coasting?

There should be a ratcheting sound, compared to say Fulcrum of Hope rear hubs. it is quiet, but is still audible.

+1. Shimano freehubs are quiet but not completely silent. They are quieter than most other brands however as you will notice if you ever ride with someone with Campy, DT or Chris King hubs.

Um, I doubt the OP is referring to freewheeling noise.

If the bearings are dry, they'll make a ticking noise. Check they're greased.

Both. I have pulled apart a rear 105 hub with loose balls and re-greased it. It was fairly straight forward. Perhaps the DA hub is not too different but I will get on the Shimano site for some info on taking it apart.

I have a feeling as I mentioned that it might have been sitting in a box for a long time and might have dry grease. Thanks for the help.