eskylid_1600 - I'm not saying you shouldn't have a go but make sure you buy all of the correct tools as you will destroy your gearset very quickly if it isn't set correctly.

Nik - good to hear that they used decent bearings, but the bad news is that if it has a consistent whine at the same speed then that is most likely an issue with the ratio itself. It'll probably be irritating more so than a problem but hopefully the oil change solves it.

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green200b - aka Alistair

The fleet:

Australia:
'80 200B GX - the green200b - hibernating
'81 RX-7 - 12A extend port - daily
'74 RX-2 - 13B bridgeport - cruiser

Europe:
'93 200SX - CA18DET - tourer

Update.
Diff is back in the car. Gearset has been lapped.
There is still a period whine or similar which is pretty loud. The clunks have gone though which is good.
I have changed the oil from 80W-90 mineral to a 85W-140 mineral during the 'bed in process' and there has been no difference in the noise. I have also added a molybdenum friction modifier to see whether that would make any difference. (Molybond 2.5), but it is still doing what it's doing.
It seems to occur around 70-80km/h under partial on and off throttle. Full throttle it's as quiet as a mouse.

So my thoughts are:
Option 1. Pull the diff out and have it looked at by someone that actually knows about R200 diffs and the best way of setting up the mesh by changing the spacers etc. Get them to play their magic and put it back in and test. This is my first thought as it's not too expensive.
I'm thinking it's just the existing guys who had no idea.

Option 2. Pull the diff out and replace it temporarily with another R200 and centre to eliminate or confirm my setup being the issue. Make a decision from there as to what to do.

Option 3. Pull the diff out and replace permanently with another R200 diff that I would buy. Replace the centre with mine and potentially the tailshaft flange (depending on the diff type). This costs me the most as I need to buy another diff.

If anyone has an R200 they can lend for a few weeks, or one for sale?
Buying another diff because this one can't be setup just doesn't make sense to me. If the mesh is setup correctly, then it should be fine.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Update!
Right, so a bit of a saga, but a solution is under way.

Upon recommendation from the forum, I spoke to Les Collins who recommended the quickest way of getting a result with minimal stuffing around was to buy another diff and change the necessary parts over. It didn't make sense to me previously, but upon Les' recommendation will actually cost me less and will be less stuffing around on both sides. It saves potentially going through a few iterations and chasing issues (based on the current symptoms and non-recorded changes made to the diff by previous diff company).

Les didn't have anything in stock, so I ended up buying another R200 3.9 Diff from a Y31 Cima from Stewart Wilkins at a reasonable price.

Les will then be transferring the pinion flange, LSD and rear cover from my old diff over to the Cima diff.
Looking forward to getting it back and back into the car.

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

So what happened with the original company?

Nothing at the moment.
I'm not taking my diff back there. They had their chance to fix it under warranty.
Doesn't mean I won't do anything though...

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Hey Nik,

I had a great experience with MadDat (Scott I think) for my diff. Might be worth a shot.

Cheers,

Trent

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1600 Build: http://ozdat.com/forum/viewtopic.php?f=59&t=22694

Trent, I am going to use Les.
Diff's will be picked up tomorrow!

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

great news Nik

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1600 Build: http://ozdat.com/forum/viewtopic.php?f=59&t=22694