The thud though is not coming from when I release the clutch. Its when I floor the gas on 2nd. Its maybe 2 seconds long which sounds like ba ba ba and the car vibrates. Sometimes it thuds, sometimes the tires make a chirp sound.

I thought it was the tires at first but the majority of you seem to be pin-pointing the clutch. I will try to focus on the clutch release and see if it solves it.

@Alberto were you thinking of the thud as the point from clutch release to contact

or are you thinking im hitting the gas faster than releasing the clutch and its causing the clutch to slip?

 

the "thud thud thud" description sounds like nothing other than wheelhop.

If you're trying to drive fast, stop shifting at 4k because that's where the fun is just starting. You aren't taking advantage of the engines powerband and your gearing by short shifting. Don't be scurred, take it to +6k, clutch in-off throttle, select 2nd, clutch out-on throttle. Simple as that.

 

Wow, for some reason, shifting into 2nd has been as smooth as butter; before it would crunch into 2nd, and I'd feel the notchiness. From time to time, I feel a notch in 3rd, and several notches going into 4th.
But I'm impressed with 2nd being much smoother.
You '06 owners feel notchiness in the gears?

 

Could he be describing the TCS? The traction control in one of my Nissan's seems to engage the anti lock brakes to keep the tires from spinning. It makes a sound similar to what he is describing.

 

In my '06 it is harder to move the shifter from 1st to 2nd than it is to get into any other gear. And when I shift into 2nd I get a 'thud' but it is during the clutching/shifting action, before I release the clutch and apply throttle in 2nd gear. It's as though 2nd gear slams into engagement. Haven't quite figured that one out yet.

 

Neh, he has a Base model Z, no TCS, no VDC.


Sounds to me like you are getting to 4000 rpm's in first, shifting, then flooring it when in 2nd. If this is the case, then you could be experiencing a bog in your engine because you are asking too much of 2nd gear. The Z really comes alive after 4000 rpm's. If you shift at 4000 from 1st to 2nd, then what you end up with is your car being somewhere between 2600 and 3100 rpm's in 2nd gear. This is fine for normal driving, but if you floor at this rpm, and the engine will struggle a bit to get back to its sweetspot at 4000+ rpm's. This could cause a shudder in the car.

The Z likes to be taken to the redline.