Rear diff started clunking
Le Mans Master
Joined: Aug 1999
Posts: 5,411
Likes: 2
From: N Carolina 08 Z51 Coupe
First, I have the clunking in my 05.
Now, if I take it into the dealer and they do their magic with a fluid change... How do we know that there isn't any permanent damage inside the diff from it clunking to begin with and that it will resurface later out of warranty?
Would we be better served if we let the clunking run its course and it restricts or locks up the diff. and we get all new guts?
Now, if I take it into the dealer and they do their magic with a fluid change... How do we know that there isn't any permanent damage inside the diff from it clunking to begin with and that it will resurface later out of warranty?
Would we be better served if we let the clunking run its course and it restricts or locks up the diff. and we get all new guts?
Hopefully the new formula will have it just right.
Banned Scam/Spammer
Joined: Aug 2005
Posts: 15,607
Likes: 3
From: 41-33 Cry it out Koko!!!
St. Jude Donor '08-'09-'10-'11
I don't agree.. Some noise from the diff plates is not going to cause any damage.. Actually .. more wear is caused by too much friction modifier being added.. Then you have slippage all the time and less lock-up when you need it... but it makes things quiet.
Hopefully the new formula will have it just right.
Hopefully the new formula will have it just right.
Are you speaking from experience, and everyone in here can rest assured that permanent damge has not happened?
Le Mans Master
Joined: Aug 1999
Posts: 5,411
Likes: 2
From: N Carolina 08 Z51 Coupe
so I have the schooling and some experience.. but this is really pretty simple.. I had this issue with my 99 C5, switched to Redline fluid and all was quiet and well.
Some groaning noise is not going to cause any problems.. The clutch packs are tight and breaking in. You get the best lock-up performance this way. The fluid change will allow them to slip more which makes it quiet but at the cost of less lock-up.
My son's M3 also had this issue.. Their service bulletin said to leave it alone as break-in will eventually occur and the noise will subside.. but they also will change the fluid out and add some modifier to make it quiet if requested.
Goon Squad King of Battle
Joined: May 2008
Posts: 118,306
Likes: 923
From: 🐑🐑🐑🐑🐑🐑🐑🐑🐑🐑🐑
St. Jude Donor '08 thru '23
Well... I was a certified SAE mechanic many years ago..
so I have the schooling and some experience.. but this is really pretty simple.. I had this issue with my 99 C5, switched to Redline fluid and all was quiet and well.
Some groaning noise is not going to cause any problems.. The clutch packs are tight and breaking in. You get the best lock-up performance this way. The fluid change will allow them to slip more which makes it quiet but at the cost of less lock-up.
My son's M3 also had this issue.. Their service bulletin said to leave it alone as break-in will eventually occur and the noise will subside.. but they also will change the fluid out and add some modifier to make it quiet if requested.
so I have the schooling and some experience.. but this is really pretty simple.. I had this issue with my 99 C5, switched to Redline fluid and all was quiet and well.
Some groaning noise is not going to cause any problems.. The clutch packs are tight and breaking in. You get the best lock-up performance this way. The fluid change will allow them to slip more which makes it quiet but at the cost of less lock-up.
My son's M3 also had this issue.. Their service bulletin said to leave it alone as break-in will eventually occur and the noise will subside.. but they also will change the fluid out and add some modifier to make it quiet if requested.
Le Mans Master
Joined: Aug 1999
Posts: 5,411
Likes: 2
From: N Carolina 08 Z51 Coupe
When my 99 was acting up.. I had it in the shop for a window motor.. So I told them to go ahead and change the fluid out to correct the noise..
The mechanic told me they added an extra bottle of a friction modifier to make sure it was real quiet..
A couple of weeks later.. I changed it out to redline without any additional modifiers and it was quiet for years.
Team Owner
Joined: Jul 2001
Posts: 21,360
Likes: 992
From: Various places in Southern California.
What they're talking about here is a clunking noise that happens during very tight turns at low speeds. Under those conditions, the limited slip differential has to allow a lot of slippage because the outside rear wheel must turn faster than the inside rear wheel. The clutches are what modulate the allowance of the varying wheel speeds and sometimes the clutches inside the differential go through a slip-stick action that creates the clunking.
It's a pretty distinctive sound. It's usually most noticeable when the car is cold, before the differential oil has heated up.
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Melting Slicks
Joined: Sep 2004
Posts: 3,488
Likes: 27
From: Long Island NY
I changed my fluid a while back (using the old GM non-synthetic oil and only 4oz of additive)... now several thousand miles later, the differential is still totally quiet on a daily basis, but IF I let the car sit for a week or more, it WILL clunk as I back out of the garage and make a sharp turn, then the noise goes away immediately.
I just purchased the new Dextron LS oil and plan to swap it in anyway. This oil was not yet available when I had changed the oil last time. The new oil looks very promising. It's cheap and easy to do. If you have not yet seen this post (link below) from the FAQ, check it out... a DIY on how to swap differential fluid, plus other differential info, all differential TSBs, etc:
http://forums.corvetteforum.com/show....php?t=1497063
Racer
Joined: Apr 2005
Posts: 297
Likes: 33
From: Peoria Illinois
I had my fluid changed and additive added under the older TSB about 15 months ago at my dealer. Now the noise is back and I am out of warranty. Will I have to pay the dealer to have the new fluid added under the new TSB or will they cover it? I have about 18K miles on a 2005.
Team Owner
Joined: Jun 2007
Posts: 31,088
Likes: 23
St. Jude Donor '08 thru '13
My .02:
Don't wait- change the fluid. Use the new stuff, not the additive.
Additive helped my 06 for about a week, then chatter came back worse than ever. It sounded like it had a Detroit Locker in the rear end. It was bad. Now it's perfectly quiet, with a good number of miles on it.
I did about 20+ minutes of figure 8's in a parking lot near my house to ensure good circulation once I put the new gear oil in.
This is a 10 minute fix in your driveway- there are two torx plugs- one to drain, one to fill. If no chunks come out when you drain, you're fine. Capacity is 1.6 qt- I overfilled mine just a bit- if it's too much, it'll burp out the vent.
If you document doing this, there is no reason to have the dealer do it. You'll save a lot of time. For me, taking the car to the dealer is much more of a PITA than just doing it at home, and knowing it's done right.
FWIW, HTH.
Don't wait- change the fluid. Use the new stuff, not the additive.
Additive helped my 06 for about a week, then chatter came back worse than ever. It sounded like it had a Detroit Locker in the rear end. It was bad. Now it's perfectly quiet, with a good number of miles on it.
I did about 20+ minutes of figure 8's in a parking lot near my house to ensure good circulation once I put the new gear oil in.
This is a 10 minute fix in your driveway- there are two torx plugs- one to drain, one to fill. If no chunks come out when you drain, you're fine. Capacity is 1.6 qt- I overfilled mine just a bit- if it's too much, it'll burp out the vent.
If you document doing this, there is no reason to have the dealer do it. You'll save a lot of time. For me, taking the car to the dealer is much more of a PITA than just doing it at home, and knowing it's done right.
FWIW, HTH.
Team Owner
Joined: Jul 2001
Posts: 21,360
Likes: 992
From: Various places in Southern California.
I had my fluid changed and additive added under the older TSB about 15 months ago at my dealer. Now the noise is back and I am out of warranty. Will I have to pay the dealer to have the new fluid added under the new TSB or will they cover it? I have about 18K miles on a 2005.
If you're handy enough to do your own oil changes, though, you can easily change the differential fluid. Check the DIY on this site. Just make sure you've got a decent hand pump to get the new fluid in and always remember to remove the fill bolt first! (Never remove the drain bolt first, because you'll be stuck if you then find that you can't undo the fill bolt.)