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Old May 20, 2012 | 09:46 PM
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Default diff noise gone

I have a 05 coupe and it had the rear end "clunk" anytime it was pulled out of the garage first thing in the morning.
I searched here on the forum and changed the fluid, replaced it with amsoil and the modifier, did some figure 8's and when I took it out in the am the noise was history.
I feel better and the car sounds better.
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Old May 21, 2012 | 02:32 PM
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Originally Posted by SUNNYD 95
I have a 05 coupe and it had the rear end "clunk" anytime it was pulled out of the garage first thing in the morning.
I searched here on the forum and changed the fluid, replaced it with amsoil and the modifier, did some figure 8's and when I took it out in the am the noise was history.
I feel better and the car sounds better.
That's exactly how I finally stopped the noise from my diff.

Tom
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Old May 21, 2012 | 11:04 PM
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There are some great people and a wealth of knowledge on this forum. I solved the same issue with some great insight from the forum.
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Old May 22, 2012 | 12:32 AM
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Where did you buy the modifier?
Thanks.
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Old May 22, 2012 | 07:17 AM
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AMSOIL Severe Gear is the real deal as I have done DIY changes on 3 pre-2009 model corvettes with great success. Severe Gear is already formulated with slip lock additive but a car already with severe chattering will benefit from a little extra added. AMSOIL also sells slip lock additive separately in a 4oz tube. JMHO.
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Old May 22, 2012 | 08:35 AM
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I got the modifier from the dealer who sells the amsoil,the additive is called "slip lock" made by amsoil.
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Old May 22, 2012 | 10:58 AM
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Thanks, gonna get this ordered tonight.
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Old May 22, 2012 | 07:25 PM
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Originally Posted by Legal Alien
Where did you buy the modifier?
Thanks.
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (Product Code SVGQT)
AMSOIL Slip-Lock Differential Additive (Product Code ADATB)

For those interested, I’m happy to offer dealer wholesale prices, about 25% below retail, for forum members via the AMSOIL Preferred Customer Program. Drop me a PM if interested.
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Old Jun 5, 2012 | 11:08 AM
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My 2007 is clattering bad! I took it to the dealer and they charged me to replace the fluid. It was WORSE after that. Could mine be too far gone for AMISOIL to work? If so, should the differential be covered under the powertrain warranty?
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Old Jun 5, 2012 | 12:29 PM
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Originally Posted by Jharms
My 2007 is clattering bad! I took it to the dealer and they charged me to replace the fluid. It was WORSE after that. Could mine be too far gone for AMISOIL to work? If so, should the differential be covered under the powertrain warranty?
Maybe not. My 06Z was chattering when my dealer told me about it during a separate service visit. They changed the fluid for free but it was before Dexron LS was introduced. Dealer said that there was a good chance the noise would come back but GM forced them to do a fluid change first before doing a clutch pack replacement. The chattering came within a month or two worse than before. In desperation to avoid major surgury on the rear end, I followed the advice here on the CF and used AMSOIL Severe Gear 75W90 plus additional AMSOIL slip lock additive. Never a problem after that day. Difference was immediate after doing the figure 8s. At one time prior to DEXRON LS being introduced, GM had a TSB that suggested using 2x the normal amount of additive. Since AMSOIL is already formulated with slip lock additive, I used only one additional bottle of additive. I would suggest you try AMSOIL and add separately 2-4 ozs of additive if your chattering is severe. Do 7-8 figure 8s in different directions in a empty parking lot afterward to work the additive in the clutch packs. If you try it, give us a report.

Last edited by GOLD72; Jun 5, 2012 at 12:31 PM.
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Old Jun 5, 2012 | 01:49 PM
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Thanks, Gold72! I may give this a try. How long has yours been "silent"? I replaced the fluid myself a few months back with standard Mobil 1 synthetic and the clatter was immediately gone...for a few weeks. It quickly came back. If using AMSOIL is a long term fix, I'm all for it! If it's just going to comeback in a few months, I'd rather fight with the dealer to replace parts (if that is a long term fix).

Does anyone know if replacing parts (would it be doing a clutch pack replacement?) would be covered under the GM powertrain warranty? I'm about to the end of that warranty so I need to act fast.
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Old Jun 5, 2012 | 07:05 PM
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Originally Posted by Jharms
If it's just going to comeback in a few months, I'd rather fight with the dealer to replace parts (if that is a long term fix).
To the best of my knowledge, it is a long term fix. The fluid needs the right properties to prevent the diff clutch plates from grabbing and releasing (e.g. chattering). There is a balance - too much slip causes some minor loss of limited slip performance. I suggest Gold72's advice to all my C6 customers unless they only track their cars, then I suggest no additive on top of what is already in the AMSOIL. The 2nd factor to consider is the shear down of the base diff fluid. AMSOIL's fluids use a high quality synthetic basestock and are very shear resistant (thus they maintain their viscosity over long periods of time). Other fluids will shear down rapidly, causing a change in viscosity and thus the diff chatter can come back.
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Old Jun 5, 2012 | 11:33 PM
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Thank you, Subdriver! I respect your opinion. PM coming your way to see what it would cost me to get my embarassing Indy Pace Car back to normal.
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Old Jun 6, 2012 | 07:14 AM
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Originally Posted by Jharms
Thanks, Gold72! I may give this a try. How long has yours been "silent"? ..........
As I recall, the car definitely had less than 20k miles and less than 2 years of ownership when I did the DIY with Severe Gear. I sold the car over 3 years later at 48k miles so it was still quiet over 30k miles with AMSOIL. Severe Gear made such a believer of me that I joined their Preferred Customer Program (buy at dealer cost) and use their tranny fluids and 5W-30 ASL motors oils in 3 vettes and one CTS Wagon. My son's 08 coupe (also pre-DEX LS factory fill) was also chattering which was resolved with Severe Gear several years ago. The 07 vert wasn't chattering but I switched it to Severe Gear also at 20k because I had the fluid on hand.
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Old Jun 6, 2012 | 07:28 AM
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Thanks, GOLD72! I'm about ready to give it a try. What products and in what quantities should I purchase to do the job?
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Old Jun 6, 2012 | 08:51 AM
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Guys....as a point of information, GM Dexron LS Gear Oil, p/n 88862624, is the later formulation that contains the corrected ratio of friction modifier. Nothing wrong with Amsoil or Royal Purple, but just another option.
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Old Jun 6, 2012 | 12:59 PM
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Originally Posted by Jharms
Thanks, GOLD72! I'm about ready to give it a try. What products and in what quantities should I purchase to do the job?
Quantity depends upon whether or not your differential has the diff cooler & recirc pump or not. The standard coupe & vert diffs (non-cooled) require purchase of 2 qts. The cooled diff like on the Z06 & ZR1 will require purchase of 3 qts. The AMSOIL products are:

Severe Gear 75W90
4 oz tube of AMSOIL Slip Lock Additive
AMSOIL hand pump (optional)

Webpage: http://www.amsoil.com/

You will need a 10mm Allen wrench. You can get this as a 10mm Allen head set into a socket for a 3/8" drive wrench which is real convenient. A pipe cheater extension maybe helpful when breaking loose the Fill plug. Otherwise a long socket wrench. Space is cramp behind the right muffler. Try to level up the bottom of the car as much as possible when you go to refill the diff with the hand pump. Its full when the fresh fluid starts draining back out the Fill port. Whether your diff arrangement needs purchase of either 2qts or 3qts, it will not take the entire purchased amount. You will still have maybe a pint or more left over. I have changed the fluid on both diff types.

Last edited by GOLD72; Jun 6, 2012 at 01:08 PM.
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Old Jun 6, 2012 | 01:05 PM
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Originally Posted by Dave S
Guys....as a point of information, GM Dexron LS Gear Oil, p/n 88862624, is the later formulation that contains the corrected ratio of friction modifier. Nothing wrong with Amsoil or Royal Purple, but just another option.
This is true. I used Severe Gear because DEXRON LS had not been introduced yet. AMSOIL and RP both include slip lock additive in their formulations. Adding it separately is only if you have severe chattering and adding more has to be done cautiously as Subdriver points out or otherwise our might over-do it and disable the positract function.
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Old Jun 6, 2012 | 04:12 PM
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Originally Posted by GOLD72
I have changed the fluid on both diff types.
Hey, have you done the cooled differential (GS) according to the service manual? It requires running the car at 'x' rpm in 2nd gear, or something like that, then shut engine off and immediately fill again until fluid comes out. I don't know how much more you can fit, due to cooler volume. Curious about your comments on that. I plan to do it by the book, which requires putting car on ramps in front and stands on rear (I already did that when swapping my '12 catted X-pipe with an '11 non-catted (OEM) one. Thx.
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Old Jun 6, 2012 | 05:18 PM
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Originally Posted by Jharms
Thanks, GOLD72! I'm about ready to give it a try. What products and in what quantities should I purchase to do the job?
Sorry for the slow response. Just got online and responded to your PM. In your case, the answer is 2 qts of the Severe Gear 75w90 and one bottle (4 oz) of the Slip Lock Additive. As noted above, that doesn't apply to all C6s.
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