LS pre-mixed gear lube has IME been a little light on the LS additive. You have to drive it to test it. I usually need to add one more full bottle of additive to quiet the plates, sometimes more.
Leaving a little bit of room in the fill, then doing a drive test like what Molakule described above is the only way to get the additive mix correct. You can get the plates to audibly “pop” at low speed with a tight enough turn.
The correct additive level is not going to be found with a phone call or email.