'07 C6 Z51 here, and I first noticed chatter while making turns backing out of my driveway. Had the latest fluid replaced under warranty at about 12k. Noise soon came back violently, this time while going slow in a parking lot while making a slight left turn (only had the steering wheel 1/4 turn to the left!). I was totally freaked out thinking my power steering was bad or something because the steering wheel felt like it was vibrating. The dealer did it again soon after. I'm at 18k now and all is well. Never had neither issue come up again. So anyone out there that had the fluid replaced/flushed once, it might be worth while to have them do it a second time.

 

I have the same question. Anyone?

 

Thunder - the noise is from the clutch packs in the rear diff. It is a ratcheting sort of sound and is usually heard when the car is cold and turning. As in pulling out of the garage 1st thing in the morning.

Just took mine to the dealer for the same issue. They say they follow a 3 step attempt at repair. 1st is to change the fluid. If it reappears they change it again. If it still makes the sound, the 3rd step is new clutch packs. If mine does it again I will let them do fluids again, but if it goes to the 3rd step I'm going to switch to the Amsoil. I don't really want them to crack things open if a different fluid will stop it.

 

Funny you should ask when it began as it just began yesterday with a bit over 8400 miles on the odometer. It's an 08 base motor. I'll probably wait till next spring to have the fluid changed.

 

Thanks. Time for a fluid change.

 

I have changed the to amsoil gear lube with no additive. GM now has built the clutch packs so that they don't require a friction modifier additive. This is what I did. Drove my car for about 1/2 hour and then drained the rear end gear case over night. I then added Amsoil synthetic manual transmission gear oil - 2.3 liters if my memory serves me correct. (Also correct oil for the Tremec transmission). After 10 minutes of driving the chatter was gone. If you still have chatter after adding the Amsoil syn gear oil, they also have a friction modifier additive called Slip Lock. Follow the directions and also talk to Amsoil.

Good luck!

The actual name on the amsoil container is Amsoil Synthetic Manual Transmission Fluid. Check there website.

 

From http://www.drifting.com:I've posted this before - seems useful

http://www.drifting.com/forums/tech-...aaz-u-s-a.html

Why does this noise occur?

The noise occurs when the L.S.D. is effective and the clutch plates are rubbing against each other. The vibration of the friction produces this noise. The noise is most likely produced when driving at low speed or backing into the garage. When the clutch plates rub together for some time it will form a perfect fit between plates and the noise will disappear.

Some new and larger L.S.D.s we make are made with larger plates to maintain more torque. Some of these larger L.S.D.s will produce some chattering noise even after the initial break in. Please do not think that chattering noise is normal when using a mechanical L.S.D. If you follow the correct installation and break-in procedures, the noise will be gone from your L.S.D. in no time.

How do I fix the chattering noise?

We understand that most car owners who use the mechanical L.S.D. are very disturbed by the chattering noise. As mentioned previously, the chattering noise comes from the friction between the clutch plates. This situation is normally caused by not doing enough break in and bad angle fit between the clutch plates.
The best to break in and remove the noise is by driving in a “figure 8” pattern as shown below for about 30 minutes and let the plates rub in to form a good fit. If this initial break in is not performed and too much torque is applied to the L.S.D. at once, the plates will form strange angles. Then the chattering noise will continue and may even cause damage to the L.S.D.



The oil used in the L.S.D. could also contribute to the noise problem. Poor quality oils contain large amount of tiny grains of metal which cause chattering noises. If noise still occurs after break in, try changing the L.S.D. oil. This usually eliminates or reduces the noise. Oil which contains large amount of added chemicals will cause noise too. Users who are especially concerned about the chattering noise could think about changing to a better quality oil such as KAAZ Powertrain Gear Oil.
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