Got my subframe back in and everything hooked back up but I need to fill the differential, I'm pretty sure its nearly empty, I lost a lost when I took the ABS sensor out

So couple of quick questions,

What weight differential oil does my standard differential 1987 300D automatic take?

What size is the hex plug in the diff (I have to go buy one, the biggest hex I have is 10mm)

Also, any tips on how to fill it? I don't have any special diff filling tools.

Thanks!

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

Soak it thoroughly in penetrating oil...for a long time...I couldn't even get the plug off with an impact wrench when I tried

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

I believe it's a 14mm hex.

Unless you have limited slip, it should take 75W-90 gear oil.

The oil should come in a bottle with a pointy spout. If you can't get the spout to the fill hole, use a hose on the bottle tip. Make sure the diff is level as you fill.

Sixto
87 300D