Do I have the correct GM part # for the limited slip posi additive. The part # in the archives is different than the # I have. I have A C Delco # 10-4003 and under that is # 88900330. This is 4 oz and I plan on putting one bottle along with Castrol limited slip 80W 90 gear lubricant GL-5. Is this Castrol as good as the GM gear oil? Thanks, Tim Barbieri
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Re: corvette posi oil additive and gear oil
Timothy,
Any API GL5 rated gear oil is fine. Any fricton modifyer labeled as such, or also called "limited slip" additive, or "posi" (TM) additive. ("Positraction" is GM's trademark for "limited slip").
Save yourself a lotta money and use Castrol, Valvoline, of any other good quality lube, as long as it's GL5. Save even MORE money, by using Castrol, or any other name brand friction modifyer. There's no reason to pop for big bucks in order to buy GM lubricants, IMHO.
Joe -
Re: corvette posi oil additive and gear oil
My 4 ounce bottle of GM "Limited Slip Differential Lubricant Additive" is part # 1052358 and the group # is 8.800
The rear axle lubricant I have is GM # 1052271 Group # 8.800, but it is only API GL4
Have it in my 68 with no problems
KurtComment
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Re: corvette posi oil additive and gear oil
How did you ascertain that the GM gear oil is "only GL-4'?
I've never seen what spec it meets, but GL-4 is not suitable for hypoid gear axles.
GL-5 was derived from the old Mil-L-2105 Specification, which is discontinued and replaced by GL-5.
DukeComment
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Re: corvette posi oil additive and gear oil
It says GL4 on the GM bottle I have, which was purchased at the local Chevrolet dealer.
KurtComment
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Re: corvette posi oil additive and gear oil
It's been awhile since I've see a bottle of 1052271, and I recall that the label had no indication of the SAE viscosity grade or GL-spec.
I am absolutely shocked to hear that the 1052271 you have is labeled GL-4.
If this is the case, I would NOT recommend it for axles or vintage manual transmissions. Use a name brand SAE 80W-90 GL-5 instead.
DukeComment
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Re: corvette posi oil additive and gear oil
Duke:
I still have a couple of bottles of GM Rear Axle Lubricant #1052271 on the shelf in my garage. The bottles state that they contain SAE 80W-90, API GL4*. The asterisk (*) refers to the following message: "This Product exceeds API GL-4 requirements and has been formulated specifically for use in certain GM axles as specified. Not all products labelled GL-4 will provide satisfactory service. Use only this product or products labelled GL-5."
I have been running this lube in my 1967 Corvette manual transmission and posi rear axle for many years without problems. However, the posi also received two bottles of the special posi additive at the same time.
LarryComment
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Re: corvette posi oil additive and gear oil
Duke,
I just e-mailed you off line
KurtComment
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Re: corvette posi oil additive and gear oil
Larry,
I have the same bottle, and I also added the GM Positraction additive a syou did.
I have had no problems. (Hope I am not jinxing myself with this statement)
KurtComment
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Re: corvette posi oil additive and gear oil
The Castrol oil I have says limited slip gear lubricant 80W 90 API GL-5, does this imply that I do not need to add the 4 oz. GM additive? Is the GM # in my first post the current and correct # for the additive? Thanks, TimComment
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Re: corvette posi oil additive and gear oil
AFAIK you still need the addtive even if the label says "suitable for limited slip axles" or something similar.
The only gear oil that I know of that has the friction modifying in the bottle is Redline 75W-90 gear oil. Their 75W-90 NS does not have the additive.
DukeComment
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Re: corvette posi oil additive and gear oil
Thanks for quoting Larry.
And, of course, thanks to GM for providing such a clear and unambiguous label. So this concoction "exceeds GL-4", but otherwise use GL-5. Yes, it's crystal clear!
If it's a GL-5, it should so state.
GL-5s are formulated with a sulfur-based EP additive, which is required for hypoid gear sets, and I have never seen a hypoid axle lubricant spec that was anything less than GL-5. This additive is what gives "gear oil" its pungent odor.
So it's okay to use 1052271 "GL-4" in Corvette axles and vintage transmissions, but if you use a commercial gear oil make sure it's a GL-5.
DukeComment
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