Many posi units will chatter when you lift the inside rear wheel. You could moderate the chatter a bit with some limited slip additive, but that will make the gear oil more slippery and in theory cut down the locking effectiveness of the diff when you do need traction.

I had an Eaton posi installed in my '02 when it was new and it will occasionally chatter when lifting the inside wheel on wet pavement, but am not really concerned. It's due for a diff oil change and I might ask for a little bit of extra additive at that time. The Ford OEM trac lock and my Eaton are both clutch type units; there are smoother gear type units on the market, but they all have their downside.

I take my chattering as a sign that my posi is still working....

And then there are pure lockers which are much more abrupt in their action--basically the outside wheel in a turn unlocks and freewheels. The lockers will be much tougher in terms of drivetrain shock.

It really shouldn't hurt anything unless you perceive the chattering as causing violent shocks to the drivetrain.

Good luck,
George