Had some spare time on my hands so I thought I'd take apart, then weld up, a spare R180, 4.375 differential that has been sitting around my garage for some time. What I found inside was strange to me. The guts of this diff are much heavier than any I've ever seen. They include a two piece gear case and lots of extra bolts to mount the ring gear. Take a look at the pics. What gives? Is this still a useful R180 for my 240Z?

Looks like a 4 pinion open carrier. You can't fit 4 pinions through a window type standard carrier so they bolt it together. Is this a newer diff? I've seen R200s with 4 pin carriers like that out of newer models.

Is this a newer diff?

I don't know John. I've had the thing for some time as it is my #2 backup 4.375 diff. I've never even used my #1 backup as the Quaife has held up so far.

The diff in question was even topped off with fluid. It has 78 painted on it so maybe it is out of a 280Z(nah, not with that ratio) but it is definitely an R-180. Today I removed the ring gear from the gear case and it bolted up perfectly to a spare welded gear case w/ bearings already installed. This setup is much lighter than the "mystery" diff so Ill go with what I know.

I'm still curious to know what it came out of - perhaps some sort of 4x4 as it had large/wide flanged out put shafts?!?!

I like that guess. Front diff from a 4x4 explains the super low ratio and the output flanges. If that's what it is, the thing probably has next to no wear on it.