Rear End Gear Oil

[burb71]

Originally Posted by Fitz

For your 1996, GM DOES recommend synthetic oil for your differential. And, that differential does use an Eaton limited Slip center section. Your problem is you thought you had a clutche Eaton Posi unit but it is, in fact an Eaton TrueTrac which uses planetary gears not a clutch pack.

Thanks Fitz...
I was going to use Royal Purple in my posi unit, now I know better.

[CUSTOM/10]

I copied this right off page 25 from Eatons Posi manual I linked from my previous post, and it clearly states either can be used, provided enough friction additive is used ! Just say-in !

Now this is out of a current manual, not a 40 yr old one !

Eaton Posi™
Quality mineral or synthetic lube with sufficient friction modifier content will ensure the smoothest operating
and longest life of your Eaton Posi performance differential. Eaton recommends GM Dexron LS or Castrol Carbon Mod SAF (Synthetic Axle Fluid) for all Posi applications. If using non-“LS” gear lube, add four ounces of General Motors “Limited Slip Axle Lubricant Additive” per one-and-a-half quarts of gear lube (GM P/N 88900330/10-4003). Additional friction modifier additive may be used to reduce LSD plate “chatter,” but do not exceed eight ounces per one-and-a-half quarts
of lube. Other brands of additives may be used. A friction modifier's purpose is to lower the static coefficient of friction (grabbing) within the clutch to match the dynamic friction (sliding) in an effort to reduce the effects of friction transition (stick, slip, chatter). Excessive amounts of a friction modifier can lower both friction values, resulting in reduction of bias ratio (performance) for plate-style limited-slip differentials such as the Eaton Posi. Many brand name gear lubes contain some limited-slip friction modifier in their formulation. If you use such a lube, additional friction modifier additives should be used sparingly to avoid accidental over-saturation resulting in performance loss.

[cdowns]

Originally Posted by burb71

Thanks Fitz...
I was going to use Royal Purple in my posi unit, now I know better.

no you dont if you think fitz knows what he is spouting bullcrap about

[SierraMtns]

Originally Posted by CUSTOM/10

Here's a link to Eatons owners manual, page 25 covers the lub specs. It does list either can be used.
Not sure if this applys to a 40+ yr old unit ?

http://www.eaton.com/ecm/idcplg?IdcS...me=PCT_1087652

The unit is new and only has 510 miles on it.

Just getting off shift and back on the forum. WOW...I missed a lot.

[Shaky]

Originally Posted by CUSTOM/10

I copied this right off page 25 from Eatons Posi manual I linked from my previous post, and it clearly states either can be used, provided enough friction additive is used ! Just say-in !

Now this is out of a current manual, not a 40 yr old one !

Eaton Posi™
Quality mineral or synthetic lube with sufficient friction modifier content will ensure the smoothest operating
and longest life of your Eaton Posi performance differential. Eaton recommends GM Dexron LS or Castrol Carbon Mod SAF (Synthetic Axle Fluid) for all Posi applications. If using non-“LS” gear lube, add four ounces of General Motors “Limited Slip Axle Lubricant Additive” per one-and-a-half quarts of gear lube (GM P/N 88900330/10-4003). Additional friction modifier additive may be used to reduce LSD plate “chatter,” but do not exceed eight ounces per one-and-a-half quarts
of lube. Other brands of additives may be used. A friction modifier's purpose is to lower the static coefficient of friction (grabbing) within the clutch to match the dynamic friction (sliding) in an effort to reduce the effects of friction transition (stick, slip, chatter). Excessive amounts of a friction modifier can lower both friction values, resulting in reduction of bias ratio (performance) for plate-style limited-slip differentials such as the Eaton Posi. Many brand name gear lubes contain some limited-slip friction modifier in their formulation. If you use such a lube, additional friction modifier additives should be used sparingly to avoid accidental over-saturation resulting in performance loss.

Thanks for tracking that down. After a couple of decades of working closely with some knowledgeable tribolgists, this makes sense to me. I just changed the fluid in my '67 Riviera with a plate posi and used Redline synthetic. I'll be leaving it in there...

[CUSTOM/10]

Yeah some of our board members are pretty intense about what they believe is correct. Nothing wrong with that, they most likely developed their knowledge from experience, what they were taught and what worked for them. I personally have never used synthetic gear lube ( Motor oil Yes ) and I believe that is superior to conventional oil ! I have an older Eaton posi in my truck that I'm re-gearing now. I plan to used conventional 80-90w with the additive, it's worked for me so far, never had a problem with it.

The only reason I would question synthetic would be based on the material of the friction discs. Some are carbon discs, and I have no idea if synthetic is compatible with them ? Anyway, the manual says you can used either, so weigh everyone’s impute, make your choice and go with it !

Gary

Originally Posted by SierraMtns

The unit is new and only has 510 miles on it.

Just getting off shift and back on the forum. WOW...I missed a lot.

[CUSTOM/10]

Hey Shaky !

What part of Maine are you from ? Love Maine, I used to go hunting every yr way up north on the Canadian boarder.

Gary

[Shaky]

Originally Posted by CUSTOM/10

Hey Shaky !

What part of Maine are you from ? Love Maine, I used to go hunting every yr way up north on the Canadian boarder.

Gary

York County. The rest of Maine calls it "Boston", but I like it. Definitely not as "Bostony" as the southern border of NH!

[CUSTOM/10]

Bostony!!! I like the solotude of Northern Maine, but I wouldn't want to live up there, and then I wouldn't want to live in Boston either.... "LOL"
Both are good places to visit though !

[SierraMtns]

Anyone use this stuff?

Also I am assuming LS additive is not needed since it says its for LS.