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Discussion Starter · #1 ·
I know this has to posted a hundred times but I can't find and I don't recall when I changed my gear oil, maybe 7 years ago. Anyway I need to change the gear oil, can someone tell me what type and amount to use when changing it. Last time I remember I put a synthetic additive but I see that some oil is already synthetic. Thanks.
 

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The general advise here is to stay away from syn. stuff in the rearend.
 

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The rear takes 2.4 quarts. You only need the GM (Or equivalent) limited slip additive if you do have one in your car.
 

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If you have a limited slip rear, do not use synthetic, use conventional 75W90 and GM Limited Slip additive. If you have an open rear, use whatever gear oil you want.
 

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Discussion Starter · #6 ·
thanks guys, I found the info in the DRIVETRAIN section. I'm just going to the stealership and getting the stuff. for some strange reason I feel like this should be authentic. I wouldn't trust aftermaket gear oil.
 

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The "no synthetic with an LSD" is a given. Wasn't the latest skinny though to use 2 bottles of additive ?
 

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The "no synthetic with an LSD" is a given. Wasn't the latest skinny though to use 2 bottles of additive ?
I haven't commented on this subject, but feel I must since it's been repeated so often.

The statement is false about synthetic. What are the facts? Has anyone documented failure/slippage with synthetic?

I have run the Eaton carrier and 3.73 gears from Dan for the last 6.5 years, with 95,000 miles running Amsoil gear oil and 1 bottle of additive at each change.

The hot-rodding retired Marine who did the gear swap for me suggested I go to Amsoil after 500 break-in miles with traditional dyno juice 80/90.

I did just that, and have swapped out the fluid 3 times (Once for new rear cover install, second for new moser axles & BRGS installed, and third to swap after I totaled my 9C1 and I swapped the rear into my current Civilian ride). I have done approximately 75% of the mileage doing city driving, and the rest during long trips to and from Austin to State College.

I have found nothing to substantiate the argument of not using synthetic from my first hand experience.
 

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I haven't commented on this subject, but feel I must since it's been repeated so often.

The statement is false about synthetic. What are the facts? Has anyone documented failure/slippage with synthetic?

I have run the Eaton carrier and 3.73 gears from Dan for the last 6.5 years, with 95,000 miles running Amsoil gear oil and 1 bottle of additive at each change.

The hot-rodding retired Marine who did the gear swap for me suggested I go to Amsoil after 500 break-in miles with traditional dyno juice 80/90.

I did just that, and have swapped out the fluid 3 times (Once for new rear cover install, second for new moser axles & BRGS installed, and third to swap after I totaled my 9C1 and I swapped the rear into my current Civilian ride). I have done approximately 75% of the mileage doing city driving, and the rest during long trips to and from Austin to State College.

I have found nothing to substantiate the argument of not using synthetic from my first hand experience.
There do seem to be plenty of people that had problems with synthetic. In my searching most people were trying M1 oil. I did find a few people that had tried Amsoil with no complaints. Because I tow a travel trailer and didn't want to constantly be changing my rear diff. oil I tried the Amsoil. It has been in there for a year or two now. I used the Severe Gear 75W-110 diff. oil and 1 tube of the Amsoil Slip Lock additive. On rare occasions I can hear my limited slip making some slight noise in a tight turn but typically it is quiet. I'm very happy with it. It made a little noise (slight groan, barely audible) a few times about 2 weeks after I changed it and I heard it again this weekend when turning into my garage after I had just given the limited slip a work out backing my travel trailer into it's parking spot where the car is going backward up hill while turning on grass. It was at least a year there with no noises at all. My 2 cents. I used Valvoline non-synthetic 80W-90 before with 1 bottle of Kendall additive with no issues previously.
 
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