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amsoil synthetic good or no good?

1004 Views 7 Replies 3 Participants Last post by  big gear head
I changed the gear lube in my 68 12 bolt w/posi today. I hear good things about amsoil products but i now hear the clutches grabbing when turning. Any suggestions or past experience with the product.
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It works great in my 12 bolt Eaton Posi... no chatter at all. Have you made hard left then right turns to slosh the lube all around inside the axle? Not sure what else might grab but if it continues, a bottle of posi additive from your Chev dealer wont hurt it. Depends alot on how it was set up too, Big Gear Head our resident axle guru will chime in Im sure.
Which Amsoil gear oil did you use? There are about 6 or more different ones now. The 75W90 Severe Gear is the one to use in a posi rear end. If you have an Auburn posi then you will have to use additive.
Thanks for the reply. I did use the 75 90 severe plus the amsoil additive. I bought this rear already done, sorry to say i am not sure what carrier it is. I looked at it several times trying to figure that out. The best id feature it has is what i thought looked like a large letter G. It has a very tight group of clutch springs (unlike eaton or the original gm) and i don't remember seeing one like it. I did run the car in circles after hearing the chatter. Maybe the amsoil doesn't like the residue form the other stuff??
amsoil is compatible with any petro product so I doubt that is an issue. If you know a good rear end guru, have it looked at to be sure its set up right too.
That would be an Auburn. The large G is their symbol. I think it is an A and a G together for Auburn Gear. The springs are grouped like this.

You will probably have to put in more additive. I have never seen an Auburn that was good with just one bottle of additive. The Amsoil Severe Gear doesn't even do the job with this one, but it does work great with the Eaton.
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Thanks again....after researching the net awhile i did see an auburn pro unit that looked the same as mine but i couldn't see the symbol on it. Would it be okay to add a different type of additive or do i need to use the amsoil?
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