Identifying Datsun R200 long nose LSD Differential

[Yarb]

Very fortunate to find this LSD R200. Need help identifying what these were actually identified as.

[HS30-H]

That looks like an R31 Skyline diff to me.

[Patcon]

3 hours ago, HS30-H said:

That looks like an R31 Skyline diff to me.

What details suggest this?

I don't have any pictures currently of the R200 LSD's I have to compare to

[HS30-H]

27 minutes ago, Patcon said:

What details suggest this?

I don't have any pictures currently of the R200 LSD's I have to compare to

Over the last 25+ years (how time flies!) I've bought something like 30 or more R200 diffs from Japan in various ratios (3.7 through 4.875 and the occasional 5.1) and many of them came from R30 and early R31 Skylines with the P9000 case casting. 

However, it's hard to pin true origin (OEM fitment) down when - in my experience - many of them were modified in period, often with upgraded LSDs (switching OEM two pinion to 4-pinion NISMO) or open diffs modified with aftermarket LSDs, rear cover swaps, output flange swaps etc.

Here are a couple of examples of diffs I imported and sold to the rally guys here in the UK and Europe

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[Patcon]

Are those cases different to the 300zx LSD cases?

Edit: from to 280 to 300zx

Edited October 22, 2023 by Patcon

[Yarb]

They look identical to me.

[HS30-H]

57 minutes ago, Patcon said:

Are those cases different to the 280zx LSD cases?

I've not dealt with many S130-series cases, but I'd expect contemporary production case castings to be very similar. Correct me if I'm wrong, but wouldn't S130-series output flange be rectangular rather than round?

The Z31 diffs I've sourced are very very similar to the R30 and early R31 diffs that I've had. Just different rear covers.

[Patcon]

I made some pictures in the shop today.

So here are two open R200's. Have the same casting number. I believe these are both 3.9's

Here is a Viscous LS from an 88 Shiro

Same casting numbers. The two limited slips I've had didn't have output flanges, since they use snap in CV axles. Rear covers vary depending on the application. Many people ditch the finned LSD cover because it requires more parts or work to fit. Would be interesting to know if the diffs you've had used the same casting...

[Yarb]

My LSD and the other two R200 have the same casting numbers. LSD is3:73 the others are 3:90

[HS30-H]

Sure, but case casting numbers are not going to identify ratios and open/LSD contents.

Yarb, if you want to identify true 'origin' ('identified as') of your diff then most of its provenance will come from the sourcing chain.

[Patcon]

That was sort of my point. If all the castings are some same over a 15 year period or so, then the only way to know what it is, is by looking inside. Output flanges and covers can change over time.

I'm not even sure how definite that is but atleast it would confirm ratios and open or LS

[Zed Head]

It's probably a 1988-1989 turbo 300ZX diff.  They're the unicorn diff for people looking for the easy LSD swap for their Z.  The only long-nose R200 LSD diff in the states.  1990 went to the short-nose.

This is from the 1989 PD FSM chapter.