Need Diff fluid recommendations

Its time for me to give my 1980 Vette some attention(52k Org miles).I need some recommendations for differential fluids and is there a better posi additive or should I just stay with the GM posi additive.

stay with the GM additive and either 85-140 or 80-90 gear oil. No special snake oils needed beyond those.

GTR1999 said:

stay with the GM additive and either 85-140 or 80-90 gear oil. No special snake oils needed beyond those.

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Thank you GTR and what would you prefer I use 85-140 or 80-90 gear oil. The car does have 52k on the rear.

Thanks

I would use 80-90.

big2bird said:

I would use 80-90.

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Thank you Jeff:thumbs:

I have stayed outta this, but in the iron diffys the Valvoline gear oil marked for posi use...

been fine in this iron shark diffy for some years now...

big2bird said:

I would use 80-90.

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In hot Southern Kalifornia? I would think you would go heavier. I need the light stuff up here in cold country.

GTR1999 said:

stay with the GM additive and either 85-140 or 80-90 gear oil. No special snake oils needed beyond those.

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That's is what I have used in my diff since 1972. It has over 350,000 miles on it

big2bird said:

I would use 80-90.

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I've used 85-140 since 78.

I used 80-140 with GM additive. Seems to be the recommendation.

Thanks everyone:thumbs:

I'm going with 85-140 & GM additive

I use Lucas 85-140 gear oil in my cars and rebuilds.