Change the original diff fluid?

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Old July 23rd, 2014, 03:31 PM
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Change the original diff fluid?

Guys...I've been "going through" the different components of my car (engine, trans, brakes, etc.) and I'm wondering if I should open up the rear end and drain out the fluid and replace it with new. My car is a '65 Cutlass with 57,000 miles (and as far as I know and can tell those are original miles). It has the conventional rear with 3.08's. What do you guys recommend...do it or let it be? I keep thinking that the fluid is 49 years old!!!

If I do it, what gear oil should I use?

Thanks.
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Old July 23rd, 2014, 03:40 PM
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If its an open rear just plain ol 80/90 wt gear oil. With a posi you will need the additive to go with it. It won't hurt to change the oil if it were original.
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Old July 23rd, 2014, 03:44 PM
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I would go ahead and change it. You will probably need a new cover gasket too.
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Old July 23rd, 2014, 04:01 PM
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Yes it should have been change about 20 years ago.
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Old July 23rd, 2014, 06:04 PM
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Thanks for the replies and advice guys...I'll go ahead and change it out.
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Old July 24th, 2014, 04:26 AM
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One more question...how much gear fluid do I need? I believe it's around 3 pints. Can someone verify so I know how much to buy. Thanks again.
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Old July 24th, 2014, 09:25 AM
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Buy two qts, it'll be enough.
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Old July 24th, 2014, 11:02 AM
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Originally Posted by JohnnyBs68S
Buy two qts, it'll be enough.
Ok...thanks.
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