Correct, .75L

From the manual:
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CAUTION: The fluid filler plug is not a fluid level plug.
CAUTION: If a thread of fluid runs/drips from the filler plug hole after refilling, the differential has been overfilled. Drain the fluid and refill with the correct amount.
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I used Land Rover fluid from this kit: https://www.roverparts.com/differentials/kits/DTCM400B/

 

Rimmer Bros states that all L322 front differentials use EP75w90 semi-synthetic. So presumably you could use several of the widely available name brand oils at auto parts stores. The Valvoline product is extreme pressure, full syn and 75w90, so it appears to check all the boxes and is readily available. The same EP75w90 lube is used in L322 rear differentials, with the possible (??) exception of locking differentials, although Rimmer claims those use that same lube as well. There's one oil capacity for L322 fronts, but the rears have three different capacities depending on year.

Ancillary Oils and Lubes

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rimmerbros.com

 

The OEM fluid is synthetic. I don't think I'd step away from that. Personally, I run OEM or Red Line in my cars, usually Red Line. I'm not really sure why I just went OEM this time, honestly.

 

Thank you all.