Diff. lock-Because I've never seen it, it doesn't exist

GM has been using the G80 Eaton locker for years, maybe decades. It's an auto locker - no switch needed. One wheel slips, the diff locks, you get unstuck, it unlocks. Easy peasy. Much better than a limited slip/positraciton, IMHO.

Only downside - it's not very tolerant of abuse. Lead-footed drivers tend to break them.