as in let it slip as much as you want w/o it melting? i think "the toyz" has an assembled delrin and metal diff but who would want the diffs to slip anyways? it would just rev out.... no power to the ground.
the mip super diffs are pretty much indestructible as long as the are tight. they have to be assembled, but there definitely worth it. i have a pair of em.
for it to be totally indestructible, you would need a gear diff for it but no one make one.