Gear Oil

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Mar 23, 2016 | 03:19 PM

hotrodjohn71

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Cross-Country

Joined: May 2015

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Gear Oil

I want to change the gear oil in my 56 f250.

Which weight should I use for the trans and the diff?

Thanks

Mar 23, 2016 | 04:41 PM

fordf348

Laughing Gas

Joined: Jan 2011

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From: near Philadelphia Pa

I tried straight 140 and it was hard shifting, went to 75/140 and found it to be better

Mar 23, 2016 | 10:09 PM

flat48f2

New User

Joined: Jan 2016

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From: Petaluma, CA

Read a test review and Amsoil/Sever Gear 75W/90 was rated best overall for the Dana 60 differential.

Nov 6, 2017 | 01:08 PM

hotrodjohn71

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Would it matter if its synthetic or not?

Nov 6, 2017 | 01:44 PM

Gertie-The '49 F2

More Turbo

Joined: Jul 2012

Posts: 545

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From: Columbus, IN

Although it shouldn't matter in the Dana, you need to be aware that if your transmission has synchronizers, you should only use GL-4 or earlier oil. Some of the GL-4 and about all the GL-5 have sulfur added as an EP lubricant. Sulfur eats the brass in the synchros.

Regarding synthetic, the molecules are smaller than conventional oils, and are thus more prone to leaking. I don't use synthetic for that reason. Seal technology wasn't very good back in the day, and even when the seals were new, they tended to seep anyway. Synthetic oils will only make the problem worse.