Differential Fluid
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Joined: Oct 2007
Posts: 1,174
Differential Fluid
I'm sure this has been asked a million times but what brand diff. fluid should I use.All the 80-90 regular and syn's seem to have additives in them including Walmart's tech brand.So do I still need the limited slip additive?Will any GL-5 work or should I buy the GM replacement for #1052271 which is #89021671 80-90.It's the additive part that throws me as I don't want to add additive if it's not necessary and it's already in the oil.Many thanks.I understand too much additive can make the clutches slip too much.(stuff I read ).Thanks in advance.
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Joined: Nov 1998
Posts: 71,087
From: Hell was full so they sent me to NJ
Re: Differential Fluid
Auburn (which I believe is what is in your 93) recommends:
I know Eaton (in my 12-bolt) also recommends only mineral based oils with additive.
Maintenance and Warranty | Auburn Gear Aftermarket
FAQ for Differentials
Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential.
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential.
Eaton Posi
Q: What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
A: Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance.
Q: What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
A: Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance.
FAQ for Differentials
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Joined: Apr 2001
Posts: 716
From: Calimesa, California. US
Re: Differential Fluid
The best differential fluid is Lubrication Engineers. It is a non-synthetic oil. Always add the Posi additive that the manufacturer calls for. Add additional magnets such as a magnetic drain plug, magnetic fill plug, epoxy magnets on the cover, etc.
Last edited by Pro Built Automatics; Mar 2, 2016 at 03:13 AM.
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Joined: Jun 2003
Posts: 1,112
Re: Differential Fluid
As Fred posts...GL5 mineral, "non-synthetic", 80-90 with 4oz of additive is what Auburn and Eaton specifies. When I had a auburn I used the GM stuff. My Eaton came with the Ford additive/friction modifier.
It is my understanding the materials used in the clutch or cone (auburn) materials do not like synthetic based gear oil.
IMHO any brand GL5 rated dino 80-90 wt oil and a bottle of the GM or Ford additive is the way to go for a limited slip differential.
It is my understanding the materials used in the clutch or cone (auburn) materials do not like synthetic based gear oil.
IMHO any brand GL5 rated dino 80-90 wt oil and a bottle of the GM or Ford additive is the way to go for a limited slip differential.
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