It is a limited slip differential. It is not the best one out there, but isn't bad for a large truck designed to be a car <IMG SRC="/board/images/smilies/icon_smile.gif"> It also uses clutches so it will wear out and need to be rebuilt to get full use out of it. It goes from being a limited slip to a open diff as the clutches go.
I blew mine out towing a wet concrete trailer (the 1 yard, haul it yourself type) taking a turn. All three of the keepers broke off on one side and one on the other side of the clutch packs and then then clutch parts broke loose and it ended up chewing up an end bearing and some seals as parts made their way down the tubes.
Also, it did okay offroad, but did lack when doing anything more than a Subaru could tackle <IMG SRC="/board/images/smilies/icon_rolleyes.gif">
If you want to keep good manners, but still want a limited slip,I have heard nothing but good about the Auburn version. Uses gears instead of clutches to it won't wear out.