I've got a 61 with a 4:11 posi. I'm requesting info on the correct gear lube. What does GM recommend using? Thanks. Hope all are having a great holiday.
Leon
Leon
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Re: differential lube
GM diff lube (now #89021671) and GM Posi Additive (#1052358). -
i have had very good luck with amsoil
rear gear lube plus the GM posi additive in posi rears. my 88 silverado which i used for towing racecars has had the same amsoil gear lube in for over 120,000 miles and the posi works fine. GM recommends the gear oil be changed every 7500 miles and the orignal factory fill lasted about that long before the posi started to chatter. back in the 60s/70s the only way we could keep a posi and the gears in a road race corvette was amsoil. i am sure the regular rear gear oils are improved now.Comment
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Re: differential lube
Leon:
What GM recommends is, of course, not always what is best for your application. You know that standards and grades have improved over the years, and what was state of the art in 1961 is now ancient history.
If you never drive your Corvette in temps below roughly 60 degrees Fahrenheit, and subject it to occasional "severe duty", then mineral based 85W-140 gear oil will provide better protection. For most duty cycles, then mineral based 80W-90 gear oil is sufficient.
The most important factor to consider here, is adding the minimal amount of "friction modifyer" which will prevent the clutches from chattering. I have no preference as to the brand. If you want to pay double the price for GM additive, then go ahead, otherwise, use another brand. Generally, a vintage banjo, like your 1961 will accept one 4 ounce tube with no chatter.
JoeComment
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