mbonness

This is the 2nd in a series of 3 polls I am conducting so we can gather more data regarding the rear diff noise issue. Please vote for the most appropriate option that corresponds to your C6 whether you have experienced this problem or not. Thanks!

ZeusC6

Wheres the poll?

mbonness

Poll is up now...

Vet

Thanks for the polls

What I'd like to know:

For those who have changed the differential fluid only AND for those who have had new clutch packs put in, how many MILES has it been SINCE this work was done? If the chatter came back, how many miles after the work was done did it come back?

Thing is, many people here who have changed their differential fluid and claim success have only put a few hundred miles on the car since the oil change. If so, this is not really an indicator of real "success". I want to hear from someone who has 15k or 25k or more miles on their differential oil change and NO noise yet... THAT to me would begin to indicate some level of "success".

My chatter first started somewhere around 10,500 miles, I changed the differential oil with the non-synthetic oil per TSB, have driven about 300 miles so far (5 cold start ups) and ZERO noise... axle is dead quiet. But... it might start chattering again next week! (Hopefully not )

I'd love to be able to know about how far we can go on the axle oil change before the chatter comes back.

My car will be at least one of the guinea pigs. I drained and refilled my differential oil 300 miles ago, and am changing it again (second time) right now... doing so in the name of performing a true full "flush". Once I button it up here, I will feel confident that I now have 100% new fresh non-synthetic fluid in the axle, and that all the old stuff is completely gone.

I will keep notes and will report back periodically... and will certainly alert all here if and when the chatter comes back.

Some have reported the chatter coming back only a short time after an oil change, but as I have pointed out before, in these cases (or most anyway) we do not know exactly WHO changed the oil, exactly WHAT oil / additive was used, etc, etc.... in other words, those who have not had success may not have had the oil change done properly per the TSB... thus invalid.

Mel 2001

06 A6 F55 Vert. Changed fluid at 1200 miles. Noise back at 6500 miles. Fluid changed again at dealer on 10-4 at 7600 miles .

mbonness

I was going to ask why you were changing your fluid again so soon if the noise had not come back, I guess that explains it. Sounds like you are more into preventative maintenance mode at this point. Hopefully if your original clutches have been seated in correctly this whole time the noise will not come back now that you have the good fluid in there.

Difficult to tell, I would hope that the dealers are mostly following the TSBs "by the book" but I would expect some variation from one dealer to the next. I was trying to keep the poll as simple as possible as per forum guidelines.

Keep the votes coming guys, I have 178 of you reporting axle chatter in the other poll and only 16 so far in this poll. I appreciate all of your valuable time in helping get to the bottom of this issue that is affecting so many of our C6s...

Tally Ho

Eight months old with 3400 miles. No noise yet. Z51 with A6.

Vet

Well, the TSB says to "flush". Everyone seems to have a slightly different definition of what "flush" means. Some feel it means merely draining a fluid and then refilling, period. Others feel it means draining, refilling, then draining and refilling AGAIN. With the latter, you are truly washing or "flushing" out the old fluid, not just draining it. So, to be on the safe side, I wanted to drain and refill twice. Figured it would be best to do it in the most "correct", clean, careful meticulous way possible. This way if and when the noise comes back, I'll truly know that I did everything I possibly could.

Once you hand over your car to strangers, you really never know what goes on. As theorized, some dealers may even put in incorrect fluid because they specifically want the extra business of changing the clutch packs... etc. You never know.

Plus, many of those who have changed the differential oil themselves have even admitted to using synthetic as opposed to non-synthetic, etc. In most cases, we really do not know how the job was done. Well... I certainly did it by the book and will report back if and when I hear any more differntial noise!

Excellent work! Thanks again for the polls!

mbonness

Interesting early results, with 51 votes in so far, just to summarize:

-The fluid change is 74% effective at eliminating rear axle chatter completely.
-20% of you have indicated you are hearing noises but have not had the TSB work done yet.

mbonness

OK we are up to 64 votes now, numbers are tracking about the same. This poll is going to close in a few days and then I will be posting one more poll to determine any correlation between axle chatter and break-in.

StarJack

Had it done last week. All is quiet now.

mbonness

Looks like the fluid change is surprisingly effective according to the results of this poll.

For those of you who are still sitting on the fence I would strongly encourage you to get the TSB work done, you should notice a definite improvement right away...

Vet

The only problem is that we do not know how many miles people have put on their cars since the fluid change was done. The noise may return in every car after a certain amount of miles.

There is another thread floating around here where two members reported the return of chatter about 2000 miles after having the oil changed. One member says he changed the oil 3 times and the noise keeps returning 2000 miles after. Not a good sign. Not sure which oil he was using but will find out... because if he was using synthetic instead of the recommended mineral, his report doesn't count.

I'm getting worried that everyone is going to start crying once they hit 2000 or so miles on their new oil. I really hope this is not the case. 2000 miles is too short an interval to tolerate. We can't be changing our differential fluid every 3 months.

As you know, I just performed a full flush and fluid change on my axle using the exact oil specified by the TSB, etc, did everything perfectly and meticulously. I drive my car normally and do not abuse it. It gets a good mix of straight highway and slower twisty driving. My car should serve as a good accurate test here... I will leave the differential alone now until the noise returns and will report back when it does... but hopefully it'll be more than 2k miles.

mbonness

I have probably put about 1K miles on since I got the service done and it's still extremely quiet. It seems logical to me that for people with improperly broken in clutches you could keep doing the fluid change ad infinitum and the noise would keep coming back, so in their case they really need the clutch replacement and that's why it's the 2nd line of defense in the TSB. Also if people insist on hammering their rear ends instead of breaking them in properly they would need to keep getting their clutches replaced.

It's certainly a complex issue, there are a lot of factors involved and a lot of moving parts (literally) but the time-sensitive aspect of it is something I'm trying to rule out for purposes of the poll, I would rather just grab a snapshot of this instant in time and simplify things a little bit, otherwise we would have to track individual C6 owners over time and gather a lot more data to really do this thing in more of a scientific fashion.

I'm hoping the next poll may shed some more light on whether or not this is truly a break-in related issue. I will try to post it this weekend after this poll expires...

KristinC6

Well, I voted too soon.

I had the fluid changed about 2 months ago (approx 1,000 miles) and it worked for a while, but now the problem is back. I'm going to take it in for part 2 of the TSB. BTW: I did break it in by the book.

Crush2

2006 A6 F55 vert

Fluid changed, only a minor reduction in chatter, then came back louder and stronger after less than 100 miles. Clutch packs then replaced, no problems since. Chris at Westside Chev. in Katy takes REAL good care of me. Only about 300 miles since packs, but I'm thinking it may be permanent fix, very pleased.

The Clevite Kid

On Saturday FB3 and I put our Corvettes (both 2006 C6's) up on my lift and drained the factory fill axle lube, and refilled with Mobil 1 75W-90 and 4 ounces of GM Limited Slip Additive, part no. 1052358. Then we did some low-speed figure 8's in the parking lot to work the new fluid with additive in between the limited slip components. The GM additive cured a chattering I had in the Auburn Limited Slip in my '84 C-10.

We figured 4 ounces of prevention were worth whatever the cure might be.


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