A poorly-adjusted clutch pack in a limited-slip will make all kinds of horrendous noises. A properly functioning locker will make noise in a corner, if it is under power. A spool makes turning a vehicle a nightmare, and nasty "scrubbing" wear is always evident after a few miles, if one looks at the tires. A quick test for the presence of a spool, is to mark the tires where they hit the ground, and drive around for a few minutes, making corners and spinning the tires a little (if possible). Park the vehicle so one tire is again sitting with its mark on the ground, and check the other tire- if the mark is in the exact same orientation as when it was marked, you have a spool. If it has moved in relation to the other tire, then you have another setup, and it might be a good idea to pull the cover off of the diff, and examine all internals. Many people forget to install the friction modifier that a limited-slip needs in order to function properly, and ruin a good diff by driving it that way.