No the "MAIN" carrier is replaced on the heavy duty style lockers. Detroit, ARB, OX, etc...
These lock, and I mean Lock solid axle to axle, both wheels spin at equal speeds.
These require more then your average tools and shade tree knowlege.
Posi's have the same princible as a
locker but have clutches instead of big metal teeth. So they will allow a little slip between wheel speeds. Very nice for any type of street use. and very good off road, just not the best thing out there. Also involve removing the carrier.
Some soft lockers, lock rite, basically replace the inside guts of the "Main" carrier. These typically can be installed by the average person.
But can be cheap in quality, durablilty, and noisy
Did that help any??