I searched the forum and it seems like the 6MT is a noisy transmission.
I really don't mind the sound as long as its not broken.

I have about 400 miles on the car and still getting used to the 6MT and infinitis clutch.

When I am standing parked or perhaps on a redlight with windows down. When I press or depress a clutch i can hear a mechanical noise from underneath the car. Its faint but I can hear sometimes. More like a thump/numb clunk noise. Is this normal?

Sometimes, when shifting gears, esp 1st to 2nd, theres a slight kick and a mechanical noise of shifting gears. Every other gear is no issues, smooth as butter.

Sometimes, when going into a gear, its smooth as butter, sometimes its a mechanical feel ( and yes i always have the clutch fully pushed to the floor )

and finally, sometimes when shifting gears, i hear them changing. I hear a lot of mechanical noise. NOT GRINDING, but clutch,shift,gear change noise. This is fairly quite noise but when you are listening you can hear it.

Perhaps im just paranoid and not used to owning a 6mt.

anyone else have these or similar issues?

 

The sound your hearing when you engage/disengage the clutch while sitting still is normal I believe. Mine does it every time. The mechanical sound coming from gear changing is probably normal too. I've always felt that Nissan's transmissions were somewhat noisy. I know I can hear what I think is my flywheel chattering while I'm idling. I used to drive a 350Z and I put Royal Purple gear oil in my tranny and I thought it smoothed the shifting up a lot; but it could have just been in my head. I'd say your car is fine though. Welcome to the forum.

 

^ +1. likely just normal gearbox operating sounds. i've gone on test drives with dealer master tech's and they all say the same thing - our gearboxes are not the quietest or smoothest out there, but they are very stout! i've test driven brand new 6MT's since i was skeptical, but it is true.

now, some 6MT are prone to premature bearing or synchro issues, but what OP describes sounds normal. just keep monitoring the sounds and if you start to hear excessive grinding or whining take it in to the dealer.

 

The 1-2 shift is most challenging on this car to get smooth. In part because there's such a huge rpm drop between the gears and also because of clutch feel - the latter of which you should have resolution to in a few days .

Some find shifting 1-2 to be easier at higher rpms. I normally don't go above 2500-3K under normal driving for this shift. Rpms have to drop as low as 1500 to be smooth when engaging 2nd (from 3Krpm). When really cold out - below 30's (F), i'll typically double clutch the first few shifts until things warm up.

 

The transmission is just alittle clunky but its stronger than hell. Not sure how much its really changed from my g35 but pretty much replace your clutch, pivot joint and throw out bearing and your hitting 450 trq with no problems.

 

This tranny is bullet proof, and very heavy duty... A side effect of this is its a bit noisier

 

Used to hear this on my 350z and it would drive me nuts. But it's normal