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  #1  
Old Dec 31st, 06, 09:45 PM
Black Z Black Z is offline
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Question What Rear End Fluid with Eaton Posi?

What brand and weight rear end fluid should I use with a new eaton posi in my 1969 camaro 10 bolt? Also what limited slip additive should I use? Thanks
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  #2  
Old Dec 31st, 06, 10:17 PM
Straight-line-69 Straight-line-69 is offline
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Default Re: What Rear End Fluid with Eaton Posi?

Eaton "strongly recommends" conventional/mineral lubes plus the GM "limited slip" additive (GM part number 10522358) for use with their posi's. Valvoline 80-90w works for me.
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Old Dec 31st, 06, 11:50 PM
Black Z Black Z is offline
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Default Re: What Rear End Fluid with Eaton Posi?

Quote:
Originally Posted by Straight-line-69 View Post
Eaton "strongly recommends" conventional/mineral lubes plus the GM "limited slip" additive (GM part number 10522358) for use with their posi's. Valvoline 80-90w works for me.
By conventional/mineral lubes does that mean no synthetic oil? What weight do they recommend, it does not say on their website?
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  #4  
Old Jan 1st, 07, 07:07 AM
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Default Re: What Rear End Fluid with Eaton Posi?

Alot of us use Amsoil Synthetic Gear lube 75w90, it has the additive built into the oil itself. While Eaton shys away from recommending Syns, (they cant seem to find the time to test their units in all the variety of lubes out there), Amsoil does warrant their product in the Eaton gears. It will run MUCH cooler and give better mileage than a dino oil. Many rear end rebuilders highly recommend the Syns.
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Old Jan 1st, 07, 07:53 AM
big gear head big gear head is offline
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Default Re: What Rear End Fluid with Eaton Posi?

I use Amsoil 75W90 Severe Gear synthetic oil in them. No problems in 10 years. GM has been using synthetic oil with Eaton differentials for around 8 years now. 2 quarts will usually fill it. Otherwise use 80W90 petroleum oil with GM or Ford additive.
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Old Jan 1st, 07, 08:18 AM
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Default Re: What Rear End Fluid with Eaton Posi?

I'm with Click and BGH. AMSOIL is what I put in mine without any problems also.
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  #7  
Old Jan 1st, 07, 08:52 AM
rogue68 rogue68 is offline
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Default Re: What Rear End Fluid with Eaton Posi?

I run the conventional + additive w/ Eaton and works great. Never even thought about synthetic. I wonder if there are any issues switching between the two?
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  #8  
Old Jan 1st, 07, 09:12 AM
Black Z Black Z is offline
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Default Re: What Rear End Fluid with Eaton Posi?

What about for the initial 500 mile breakin period? Would it be like an engine breakin period where it is recommended to use only conventional oil, no systhetics? Do all of the amsoil oils have the limited slip additive in it already?
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Old Jan 1st, 07, 09:31 AM
ept000 ept000 is offline
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Default Re: What Rear End Fluid with Eaton Posi?

I used Redline synthetic and it chattered like crazy. Changed to Valvoline and the GM additive and it's perfect now.
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Old Jan 1st, 07, 09:37 AM
Black Z Black Z is offline
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Question Re: What Rear End Fluid with Eaton Posi?

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Originally Posted by ept000 View Post
I used Redline synthetic and it chattered like crazy. Changed to Valvoline and the GM additive and it's perfect now.
If it chattered you probably did not use an oil with limited slip additive?
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Old Jan 1st, 07, 09:43 AM
big gear head big gear head is offline
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Default Re: What Rear End Fluid with Eaton Posi?

I have always used Amsoil from the beginning with no problems. Only the Severe Gear oil has the additive. This replaced the old Series 2000, which also had the additive.
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Old Jan 1st, 07, 09:55 AM
Black Z Black Z is offline
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Default Re: What Rear End Fluid with Eaton Posi?

I am thinking of trying the Redline Synthetic 75-90W GL-5 with friction modifier? Would that be a good choice?
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Old Jan 1st, 07, 11:21 AM
Hogdaddy Hogdaddy is offline
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Default Re: What Rear End Fluid with Eaton Posi?

Quote:
Originally Posted by Straight-line-69 View Post
Eaton "strongly recommends" conventional/mineral lubes plus the GM "limited slip" additive (GM part number 10522358) for use with their posi's. Valvoline 80-90w works for me.
I just put a new 8.5 Eaton posi in and the instructions said mineral lube only and no where did it say its ok uses synthetic so have they not upgraded the instructions included with these posi's?
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  #14  
Old Jan 1st, 07, 12:11 PM
ept000 ept000 is offline
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Default Re: What Rear End Fluid with Eaton Posi?

Quote:
Originally Posted by Black Z View Post
If it chattered you probably did not use an oil with limited slip additive?
No, the bottle said "for limited slip differentials" right on it. The chattering stopped the day I switched to Valvoline. Redline probably makes great products, but the Eaton posi defintely does not like it. I called Eaton a while back and asked why they don't recomend the synthetic oil and they said it was "too slippery" and it caused thier unit to chatter. I know lots of you guys and gals are using Amsoil, and like it. I will stick with Valvoline because it works, and it's not worth my time to "try" something else.
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  #15  
Old Jan 1st, 07, 12:25 PM
olympic69 olympic69 is offline
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Default Re: What Rear End Fluid with Eaton Posi?

Quote:
Originally Posted by ept000 View Post
No, the bottle said "for limited slip differentials" right on it. The chattering stopped the day I switched to Valvoline. Redline probably makes great products, but the Eaton posi defintely does not like it. I called Eaton a while back and asked why they don't recomend the synthetic oil and they said it was "too slippery" and it caused thier unit to chatter. I know lots of you guys and gals are using Amsoil, and like it. I will stick with Valvoline because it works, and it's not worth my time to "try" something else.
Thats kinda bizzare- I thought the chatter was the result of _innadequate_ lubricity/ film strength, and the clutch packs grabbing instead of slipping as they should, albeit under the high pressure of the pre-load springs and side gear forcing under load. That is why it is critical that limited slips use an extreme pressure (EP) lube or additive, otherwise the clutches will be damaged.

I think I would go with the consensus product(s) listed earlier in this thread- that being the Amsoil severe gear product which others have used with good result- in other words, you dont need to experiment!

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