Differential lube confustion
Thread Starter
Racer
Joined: Jul 2010
Posts: 262
Likes: 0
From: Jefferson City Missouri
Differential lube confustion
My o2 has a leaky butt and over the years has lost about 10 oz of oil. I topped it off with some Castrol brand. It was the basic rear end oil of the proper weight. As a result of adding that much have I screwed up the necessary mix of oil and additive to the degree that I may hurt something? Secondly there are numerous posts on what people use some saying include additive others say don't. Some say it is in some of the oil and enough while others are saying there is not enough in it and to add more.
Question.... is the mix I have now ok for the time being and not hurt anything? Secondly, if I change the fluid... is there any real agreement on what to replace it with?
Question.... is the mix I have now ok for the time being and not hurt anything? Secondly, if I change the fluid... is there any real agreement on what to replace it with?
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Take the car to a parking lot and do some slow figure 8's. If it needs additive, the clutches will chatter. Adding too much additive will effectively eliminate the limited slip capability of the clutches so don't add more than required.
Some of the aftermarket oils do have the limited slip additive in it as it comes from the bottle. Redline 75W-90 has it, Redline 75W-90NS does not. So the answer to this question is very specific to the oil being used.
Some of the aftermarket oils do have the limited slip additive in it as it comes from the bottle. Redline 75W-90 has it, Redline 75W-90NS does not. So the answer to this question is very specific to the oil being used.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Why not just change it at this point and be done with it?
Use the fluid spec'd in the service manual: SAE 75W-90 either with 4 ounces of limited-slip additive OR buy the gear oil with the limited slip additive already in there; for example, Mobile 1 is labeled SAE 75W-90 LS
As for brands, the debate will always rage, but any quality gearl lube will do...
Use the fluid spec'd in the service manual: SAE 75W-90 either with 4 ounces of limited-slip additive OR buy the gear oil with the limited slip additive already in there; for example, Mobile 1 is labeled SAE 75W-90 LS
As for brands, the debate will always rage, but any quality gearl lube will do...
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Why not just change it at this point and be done with it?
Use the fluid spec'd in the service manual: SAE 75W-90 either with 4 ounces of limited-slip additive OR buy the gear oil with the limited slip additive already in there; for example, Mobile 1 is labeled SAE 75W-90 LS
As for brands, the debate will always rage, but any quality gearl lube will do...
Use the fluid spec'd in the service manual: SAE 75W-90 either with 4 ounces of limited-slip additive OR buy the gear oil with the limited slip additive already in there; for example, Mobile 1 is labeled SAE 75W-90 LS
As for brands, the debate will always rage, but any quality gearl lube will do...
Instructor
Joined: Oct 2009
Posts: 159
Likes: 0
From: Springfield MO.
I agree. Just go ahead and change it.... I run mobil 1 full synthetic 75w-90 with 1 bottle of GM limited slip/friction modifier additive. I think it's around 4oz. I wouldn't trust just any limited slip additive. These differentials are very picky.... Haha. Just my 2 cents.
Tech Contributor
Joined: Aug 1999
Posts: 16,376
Likes: 404
From: Should this thoughtful, valuable contribution meet with no acknowledgement or 'thanks' this post----
your GM dealer now has it with the additive mixed in...that would be a great choice for your car now....but you should start from scratch with a full fill.
Tech Contributor
Joined: Jan 2007
Posts: 19,564
Likes: 1,207
From: Dyer, IN
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