Rear Diff Additive!!!
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Teching In
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Rear Diff Additive!!! So, me being new too the site and just bought my first Camaro I had to share this. So yesterday after work, I'm pulling into a parking spot and start to hear a clunking noise coming from what appeared to be the rear end when I make sharp turns to park.....obviuosly not good
. I immediately set up an appointment with my mechanic. I tell him that I just bought the car and know very little about it at this point, he checks out the rear end and notices that the differential cover is fairly new, so he suspects the previous owner had replaced it. Long story short, he drains out the fluid and opens it up, no damage to anything, replaces the fluid, along with the additive and......all is quiet again
, he thinks the previous owner may have used the wrong oil and no additive. I know many of you probably already knew this info, but it's something new for me. He stated that the additive should be added!!! Thanks for reading.
. I immediately set up an appointment with my mechanic. I tell him that I just bought the car and know very little about it at this point, he checks out the rear end and notices that the differential cover is fairly new, so he suspects the previous owner had replaced it. Long story short, he drains out the fluid and opens it up, no damage to anything, replaces the fluid, along with the additive and......all is quiet again, he thinks the previous owner may have used the wrong oil and no additive. I know many of you probably already knew this info, but it's something new for me. He stated that the additive should be added!!! Thanks for reading. Last edited by Russ8993; Aug 11, 2017 at 10:35 AM.
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From: Schiller Park, ILL Member: #317
You mentioned the car being a '99 "RS"...is this a V6 car? Or a Z28 with the SAP (Sport Appearance Package)? Either way, I'm assuming it has a limited slip rear based on your description of the issue.
As for the V8 models, the additive is not a requirement for the '99+ cars as they use a Torsen LSD (not a clutch-type.) The Torsen is also not as sensitive to fluid type (though 75w90 synthetic is recommended), unlike the earlier Auburn (cone-clutch style.) If you have an Auburn LSD, then you'll specifically want to use a conventional (not-synthetic) lube (80w90 recommended) and a 4oz bottle of GM LSD additive. But you would only have an Auburn in a '99 car if someone changed it at some point (as '98 was the last year for the base Auburn, unless you have an SS that was ordered from SLP with the optional upgrade Auburn, but you said it was an "RS", not SS, so this should be ruled out.)
As you bought the car used, and it seems to have a new rear end cover, it's certainly possible that the guts may have been swapped/changed, or that the entire rear is not original to the car. If adding the additive really made that much difference, it sounds like you somehow have an Auburn LSD as, again, Torsens just aren't that sensitive to the additive. Or perhaps the issue was low fluid or just the wrong grade/weight, and the additive really had nothing to do with the improvement.
As for the V8 models, the additive is not a requirement for the '99+ cars as they use a Torsen LSD (not a clutch-type.) The Torsen is also not as sensitive to fluid type (though 75w90 synthetic is recommended), unlike the earlier Auburn (cone-clutch style.) If you have an Auburn LSD, then you'll specifically want to use a conventional (not-synthetic) lube (80w90 recommended) and a 4oz bottle of GM LSD additive. But you would only have an Auburn in a '99 car if someone changed it at some point (as '98 was the last year for the base Auburn, unless you have an SS that was ordered from SLP with the optional upgrade Auburn, but you said it was an "RS", not SS, so this should be ruled out.)
As you bought the car used, and it seems to have a new rear end cover, it's certainly possible that the guts may have been swapped/changed, or that the entire rear is not original to the car. If adding the additive really made that much difference, it sounds like you somehow have an Auburn LSD as, again, Torsens just aren't that sensitive to the additive. Or perhaps the issue was low fluid or just the wrong grade/weight, and the additive really had nothing to do with the improvement.
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From: Schiller Park, ILL Member: #317
Regardless, you wouldn't have a limited slip rear unless you have a Y87 car or the rear has been swapped/modified. If it's still an open differential, then the additive would not have done anything to help with any type of noise - meaning that either you had a low fluid condition, or entirely the wrong type of lube, or something else is wrong with the rear and the fluid change has just temporarily masked it.
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My sticker says "1F87" After talking more to the shop that did the work, they said the fluid wasn't low, but he was pretty sure the previous owner used the wrong fluid, and being that the cover and bolts had been replaced, could be a swap, oh well, for now all is good!!!
