What weight of gear oil do I use in an 84 300D?

moved for better answer.

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1985 300SD
1983 300D
2003 Volvo V70

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I use 75/90 semi-synthetic....

Works for me....

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W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

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I have searched for the same question.

Spec calls for '90 weight Hypoid gear oil'. You can find dino versions of this at Autozone etc.

Most use 75W-90 Mobil 1 Synthetic Hypoid Gear Oil. Also at AutoZone etc. After reading all of the info on oil here, this is what I use. Its 5 bucks more to use the full synthetic.

dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

AMSoil 75w-90 full synthetic

redline racing 75-90 full synthetic with chemical additives to increase gear life and quiet down everything about 30$ a quart..... lol i wish im using 75-90 dino oil

While I am a big proponent of using full synthetics (Mobil, Amsoil, Redline) in the engine and tranny, I have NOT had great results in Mercedes differentials. I had several develop gear whine about 20-50kmi after switchnig to synthetics. It could be coincidence, but I've decided to no longer use synthetic in my diffs. I'm sticking with the MB fluid and changing every 25kmi or so. YMMV, etc, etc.

If you have LSD, ASD, or 4Matic, use ONLY the factory fluid from the dealer.

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I put 80-90w in mine. All that the local auto parts store had in stock.

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Normally i use 80W-90 (Mobilube HD or GX), but now have gone to 85W-140 (same price) should handle hard driving better than lower grade oil.