What's this "clacking" noise?
 

Under hard acceleration and under boost, I hear a brief ratcheting or clacking noise in the engine or drivetrain when I abruptly take my foot off the pedal. I can easily reproduce this when I accelerate hard to about 4-5k RPM and quickly take my foot off the pedal.

It is similar to the brief clacking noise heard on some of the VQ37s on an engine start, which I also hear sometimes.

Since you have boost, I assume you have tweaked the fuel injection. My first guess is that you are not stopping fuel flow fast enough, you're getting unburnt fuel into the exhaust system, and you are hearing muffled explosions. But that's just a guess.

I've heard exhaust popping noises, but it sounds like valvetrain noise.

Backfire and what OP is claiming is 2 totally different noises.
Sure is funny to hear that under hard acceleration. Can't really guess the problem other than sumthin moving while under load. If its happening around 4-5k rpm I'm sure that's where ur torque peaks at and that's not good to hear that noise at that moment. Good luck getting it figured out!

Thanks, I don't hear it under moderate acceleration or when I ease up on the pedal.

Oh, what's also interesting is when I'm in the higher gears when pushing the motor and abruptly taking my foot off the pedal at low revs like < 4k RPM. I can hear this noise, so it doesn't have to be in the lower gears.

[EDIT] I remember now. I was testing for clutch slippage by briefly flooring it in high gear 3-4k RPM around 40 mph.

could be your rear axles clicking. mine are doing it during acceleration and deceleration.

Do you have a vid of the noise.?

Do you hear the metallic clacking sound on startup? Some G owners reported this as well. It's a similar sound. Just push it a little hard in the high gears and abruptly let off the throttle.

Hey fuct I also hear my rear axels clicking upon acceleration and deceleration show i be worried and take it in for service? Or are these noises common for the Z?

wait........you don't transport chickens in your car, do you?

clacking != clucking

I had the same noise - took it into the dealer, and the service manger says it's a very common problem. The rear axles need to be removed, regreased, then retorqued. You should have no issues if you have a warranty with the car or anything. They took my car no questions asked, and I was done in an hour or so.

I'm hearing the clunking noise, which is referenced in my other thread. I have to get it checked on my next oil change.

Cool thanks for the info! I do have warranty on my car so on my next
Oil change I'll ask them to check it out.

u joints, flexplate/flywheel loose or diff bushing, would be my guess.
I had this issue, only in first gear.. ended up to be my u joint in the rear.