Ominous creak from rear end
07-05-2008, 01:39 AM
#1
Le Mans Master
Thread Starter
Ominous creak from rear end
My C6 has begun emitting a loud metallic snap under moderate torque reversals. For example, if I set off in 1st by abruptly releasing the clutch, it will make the noise. It won't do it again until I wind up the drivetrain the other way, say by abruptly releasing the throttle in a low gear. The next time I goose it, it makes the noise, and so on.
The sound it coming from somewhere in the back, and is especially noticeable with the windows down as I drive alongside a wall or in a tunnel -- quite unlike other noises, such as LSD chatter, which are as loud (or louder) inside the car as they are outside.
The noise -- which again is sharp and sudden and metallic, is quite different from LSD groaning/chatter, or general gearbox rattling (as when driving around under light throttle in a parking lot). Nobody would describe it as a "clunk." It's more like a "snap" or "crack." It's also getting worse.
It doesn't correlate at all with going over bumps or around corners. I can't get the noise to occur by rocking the car around on its suspension. It only happens under torque reversal. The lugnuts are tight and the big axle nuts are tight, too. The CV boots are clean and there are no apparent oil leaks from the transmission or differential.
Has anybody had this problem? Was it in the torque tube? The transmission mounts? The differential? The half-shafts? Frankly, it sounds a lot like the clicking noise from a cracked CV joint, but it doesn't do it every revolution.
The sound it coming from somewhere in the back, and is especially noticeable with the windows down as I drive alongside a wall or in a tunnel -- quite unlike other noises, such as LSD chatter, which are as loud (or louder) inside the car as they are outside.
The noise -- which again is sharp and sudden and metallic, is quite different from LSD groaning/chatter, or general gearbox rattling (as when driving around under light throttle in a parking lot). Nobody would describe it as a "clunk." It's more like a "snap" or "crack." It's also getting worse.
It doesn't correlate at all with going over bumps or around corners. I can't get the noise to occur by rocking the car around on its suspension. It only happens under torque reversal. The lugnuts are tight and the big axle nuts are tight, too. The CV boots are clean and there are no apparent oil leaks from the transmission or differential.
Has anybody had this problem? Was it in the torque tube? The transmission mounts? The differential? The half-shafts? Frankly, it sounds a lot like the clicking noise from a cracked CV joint, but it doesn't do it every revolution.
07-05-2008, 02:56 AM
#2
Le Mans Master
Thread Starter
It can't be the torque tube
It's got to be downstream of the torquetube/driveshaft, because after the car makes the noise in 1st, either one of the following torque applications will cause it to recur: 1) abruptly letting off the throttle in a low gear while driving forward, or 2) abruptly setting off in reverse.
As far as the driveshaft is concerned, setting off in reverse is the same as setting off in 1st.
As far as the driveshaft is concerned, setting off in reverse is the same as setting off in 1st.
07-06-2008, 04:19 PM
#3
Race Director
Something is obviously coming loose. May be the mounts or on one of the cases. The problem is that it could be anything. If it were my car, I would get it to the dealer and stop driving it.
