Right Rear Thump!
Thread Starter
Racer
Joined: Apr 2004
Posts: 276
Likes: 0
From: McDonough GA
Right Rear Thump!
My wifes 2004 coupe has a loud thump coming from the right rear. I heard it once myself. Sounded like a briefcase or something fell over in the back. We just backed out of the drive, drove about 1/4 mile. Made a right turn and BAM. Didn't do it the rest of the evening and of corse it won't do it for the dealer eighter. It happens at least once a day.
Has anyone had a this happen to them and if so what fixed it? I'm thinking the differential.
Thanks!!
Has anyone had a this happen to them and if so what fixed it? I'm thinking the differential.
Thanks!!
Racer
Joined: Nov 1999
Posts: 378
Likes: 0
From: C1 C2 C3 C4 C5 Iowa
Did you?
Have you changed the differential fluid lately? And if so, did you add the proper amount of GM Posi fluid?
Without the additive, it will skip/slip with (sometimes) a very audible noise.
Good luck -
Without the additive, it will skip/slip with (sometimes) a very audible noise.
Good luck -
Race Director
Joined: Nov 2003
Posts: 12,346
Likes: 5
From: Mustang OK
Sounds like the somewhat common phenomenon often referred to here as “oil canning”. The panel behind the passenger’s seat may sometime flex much like when one pushes on the bottom of an oil can, thus causing the thumping sound. To me it sounds much like someone throwing a tennis ball against the right rear quarter panel. Our car did it on occasion when new, but we haven’t heard in some time now. In ours, it usually happened after driving the car a short distance and didn't happen again until the next time we drove the car. Like ours, It may lessen or go away with time. If you can get the Forum search feature to cooperate, you may be able to find several threads on this topic. Good luck with yours. 
Last edited by GrayC5; Feb 12, 2005 at 10:06 PM.
Melting Slicks
Joined: Mar 2004
Posts: 3,365
Likes: 0
From: Farmers Branch TX
Cruise-In VI Veteran
St. Jude Donor '09
When I got my car originally, it had the right rear thump, it went to the dealer I dont know how many times and got the old, "we dont hear it" so I just gave up, kept driving it, thumping along, then eventually, it just went away. Until I got rear ended and the plastic tub for the rear was replaced, now I am the proud new owner of a thump, so hopefully they all go away with a little time.
---Chris
---Chris
Safety Car
Joined: Aug 2004
Posts: 3,992
Likes: 3
From: Pleasanton CA
St. Jude Donor '10-'11-'12, '14-'17,'21, '25
Originally Posted by GrayC5
Sounds like the somewhat common phenomenon often referred to here as “oil canning”. The panel behind the passenger’s seat may sometime flex much like when one pushes on the bottom of an oil can, thus causing the thumping sound. To me it sounds much like someone throwing a tennis ball against the right rear quarter panel. Our car did it on occasion when new, but we haven’t heard in some time now. In ours, it usually happened after driving the car a short distance and didn't happen again until the next time we drove the car. Like ours, It may lessen or go away with time. If you can get the Forum search feature to cooperate, you may be able to find several threads on this topic. Good luck with yours.
I heard this a lot in the 1st 4000 miles. Have not heard it in the last couple thousand.
Race Director
Joined: Jun 2000
Posts: 13,733
Likes: 66
From: Hurst, TX USA
I just turned 6K on mine and I still get an occasional hollow thunk from behind the driver's seat. It always happens when I am going straight and within 5 minutes of starting out from my garage in the morning. It never happens on the way home from work... I thought it night be that the guys that installed my Z06 Tis didn't torque the rear sway bar correctly, but reading above I'm not so sure now.
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Race Director
Joined: Sep 2004
Posts: 12,071
Likes: 0
From: Hoover Alabama
Originally Posted by Today's problem is..
When I got my car originally, it had the right rear thump, it went to the dealer I dont know how many times and got the old, "we dont hear it" so I just gave up, kept driving it, thumping along, then eventually, it just went away. Until I got rear ended and the plastic tub for the rear was replaced, now I am the proud new owner of a thump, so hopefully they all go away with a little time.
---Chris
---Chris
Le Mans Master
Joined: May 2004
Posts: 7,825
Likes: 0
From: Manassas VA
Mine will still do it every now and then, and I always check the side/rear view mirrors to see what I ran over!
Once, after miles of trying to figure it out, I pulled the e-brake up, and "THUNK!!" I reset and re-pulled the e-brake and it set.
Just another one of those mysteries of the C5 I guess!
Once, after miles of trying to figure it out, I pulled the e-brake up, and "THUNK!!" I reset and re-pulled the e-brake and it set.
Just another one of those mysteries of the C5 I guess!
6th Gear
Joined: Feb 2005
Posts: 6
Likes: 0
From: Maine
Just to chime in.......... I also have a 2004 coupe. I was convinced my neighbor was throwing a tennis ball at me every time I drove by his house. The car makes this sound almost every time within the first mile after it has sat overnight. I am suspicious of the interior vent baffle that is in the rear area behind the carpet or possibly it has something to do with the fuel tanks..... I know they are connected and possibly they are to blame.
Drifting
Joined: Apr 2004
Posts: 1,937
Likes: 3
From: Jacksonville Florida
I had just over 13k miles on my 04 coupe and I heard thumping sound (thump...thump) right rear in about 1/2 to 1 mile out of the garage. Hope someone can figure out what causes it and where it's actually coming from. It's very disburbing sometime.
Le Mans Master
Joined: Dec 2001
Posts: 7,788
Likes: 6
From: Winchester TN
Cruise-In III Veteran
Cruise-In IV Veteran
Cruise-In V Veteran
St. Jude Donor '03-'04-'05-'06-'07-'11
Originally Posted by GrayC5
Sounds like the somewhat common phenomenon often referred to here as “oil canning”. The panel behind the passenger’s seat may sometime flex much like when one pushes on the bottom of an oil can, thus causing the thumping sound. To me it sounds much like someone throwing a tennis ball against the right rear quarter panel. Our car did it on occasion when new, but we haven’t heard in some time now. In ours, it usually happened after driving the car a short distance and didn't happen again until the next time we drove the car. Like ours, It may lessen or go away with time. If you can get the Forum search feature to cooperate, you may be able to find several threads on this topic. Good luck with yours.
In fact, I was even remembering him saying it sounded like a tennis ball thumping the car!
For my50thvette - try leaning the seatback forward to allow you to get access to the panel behind the seatbacks, and then firmly press your palm around in different locations on the panel behind the seat -
You may find a spot that causes the noise...
Just beware not to drill or screw into the panel, the gasoline tanks reside behind it in close proximity...
best regards -
mqqn
Last edited by mqqn; Feb 15, 2005 at 08:45 PM.
