Differential Fluid
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Pro
Joined: Apr 2007
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From: Orlando Florida
Differential Fluid
I went to the dealer to pick up some Differential Fluid for my 93.
I told the guy at the parts counter I wanted 2 bottles of 80w90 GL5 GM part # 12345977 and 2 Bottles of the additive GM part # 1052358.
First he told me that part # 12345977 was replaced with part # 89021669, Does this sound correct to anyone? He also told me I only needed on bottle of the additive and 3 of the 80w90 oil. I told him this was incorrect and for him to ask the mechanic who works on Corvettes. He came back and told me I was correct I only need two and two. I have read on the Forum that many use the 75w 90 weight oil. In my manual it shows the 80w90. Anyone have any info to add ?
I told the guy at the parts counter I wanted 2 bottles of 80w90 GL5 GM part # 12345977 and 2 Bottles of the additive GM part # 1052358.
First he told me that part # 12345977 was replaced with part # 89021669, Does this sound correct to anyone? He also told me I only needed on bottle of the additive and 3 of the 80w90 oil. I told him this was incorrect and for him to ask the mechanic who works on Corvettes. He came back and told me I was correct I only need two and two. I have read on the Forum that many use the 75w 90 weight oil. In my manual it shows the 80w90. Anyone have any info to add ?
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I have always used 80/90 weight gear oil and one 4 oz bottle of GM posi lube. Then I go do my figure eights to work it around the clutches.
Racer
Joined: Aug 2005
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From: State of Confusion
You are correct on all accounts. The manual does suggest 80w-90 dino lube with the posi additive. I don't believe that I have seen a synthetic 80w-90, only 75w-90 or 75w-140. You might be able to find it from one of the "boutique" lube oil blenders. The synthetic will give you a little bit of a performance increase, although you probably won't feel it. The synthetic will definitely give you better protection and most of the synthetic comes with posi additive in it already, which simplifies things a little. The lower viscosity isn't a bad thing, as a matter of fact GM has been putting 75w-90 and 140 synthetic in there brand new rear wheel drivers for quite some time now, my '02 Tahoe came that way. They have done this for the additional fuel economy.
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Pro
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From: Orlando Florida
You are correct on all accounts. The manual does suggest 80w-90 dino lube with the posi additive. I don't believe that I have seen a synthetic 80w-90, only 75w-90 or 75w-140. You might be able to find it from one of the "boutique" lube oil blenders. The synthetic will give you a little bit of a performance increase, although you probably won't feel it. The synthetic will definitely give you better protection and most of the synthetic comes with posi additive in it already, which simplifies things a little. The lower viscosity isn't a bad thing, as a matter of fact GM has been putting 75w-90 and 140 synthetic in there brand new rear wheel drivers for quite some time now, my '02 Tahoe came that way. They have done this for the additional fuel economy.
When I asked the dealer about using synthetic he told me no stick with what was put into the car from the factory. Yesterday I called another dealer and he told me the same thing. He also said the #89021669 was the replacement for 12345977 and it was the newer improved oil. I get so many different answers it's hard to decide what the best thing to do is. (one thing I have decided on that i'm going to use the Amsoil in my transmission).
Safety Car
Joined: May 2006
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From: Salem NH
If you go with aftermarket gears (richmond, for example) I think 75/140 is what they recommend.
I think I used two tobes of the posi additive. I've yet to see my posi unlock, not sure if thats good or bad..
-- Joe
I think I used two tobes of the posi additive. I've yet to see my posi unlock, not sure if thats good or bad..
-- Joe
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I also used 2 bottles of the posi additive. If the original GM part number had been superceded by another, the new stuff should work fine. Stay with the 80W-90 GL-5 oil
There's no reason to go with synthetic gear oil unless you are using the car for some sort of high performance driving like drag racing, frequent track days, or lots of autocross events.
There's no reason to go with synthetic gear oil unless you are using the car for some sort of high performance driving like drag racing, frequent track days, or lots of autocross events.
Racer
Joined: Nov 2007
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From: Cicero IN
Thanks for you reply!
When I asked the dealer about using synthetic he told me no stick with what was put into the car from the factory. Yesterday I called another dealer and he told me the same thing. He also said the #89021669 was the replacement for 12345977 and it was the newer improved oil. I get so many different answers it's hard to decide what the best thing to do is. (one thing I have decided on that i'm going to use the Amsoil in my transmission).
When I asked the dealer about using synthetic he told me no stick with what was put into the car from the factory. Yesterday I called another dealer and he told me the same thing. He also said the #89021669 was the replacement for 12345977 and it was the newer improved oil. I get so many different answers it's hard to decide what the best thing to do is. (one thing I have decided on that i'm going to use the Amsoil in my transmission).
89021677.
Bruce
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I've been using Red Line heavy shockproof gear oil 75W90 for mine with road racing use. It has additive in it and I do not add more. I change it every year or every two years depending on track use.
Melting Slicks
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From: AZ
My rear end builder; long time, reputable shop who does Vettes, vipers and HD vehicles claims that non-synthetic lubes better, but was okay with the synthetic I choses due to the heat from the 3" pipes RIGHT below the diff.
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YES it is. I run all Amsoil porducts in my car simply because the specialty shop that I take it to is a dealer. We first tried just the the synthetic in the rear diff however within 20 miles it began to chatter on sharp right hand turns. Drove back to the shop. We sucked out some of the diff fluid and put in two (at my insistance) small bottles of the additive and within 5 mi the chatter was gone never to reappear. I've put 50K+ miles on my 95 over the past 3 years or so and never any problem with the rear end. I had the fluid changed out after 30K and it will soon be ready for a second change.
For what its worth, I drive my car every day.
For what its worth, I drive my car every day.
Pro
Joined: May 2006
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From: Pittsburgh PA
YES it is. I run all Amsoil porducts in my car simply because the specialty shop that I take it to is a dealer. We first tried just the the synthetic in the rear diff however within 20 miles it began to chatter on sharp right hand turns. Drove back to the shop. We sucked out some of the diff fluid and put in two (at my insistance) small bottles of the additive and within 5 mi the chatter was gone never to reappear. I've put 50K+ miles on my 95 over the past 3 years or so and never any problem with the rear end. I had the fluid changed out after 30K and it will soon be ready for a second change.
For what its worth, I drive my car every day.
For what its worth, I drive my car every day.
Good enough for me!
Pro
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