2005 G35x Auto.

When going over imperfections in the road, the gear sifter shakes noticeably. Giving symptoms of a worn tranny mount. I took the tranny mount out and it looks good. So that's not it....

Also, the car gives bad engine mount symptops. When you gas it hard, then let go it does feel like the engine shifts/lifts a bit and then drops/returns to its resting position.

is there any way to inspect the mounts without actually removing them?

how many engine mounts are there 3? is it three? is the one in the front also the air bag sensor?

any tutorials out there?

 

If it's an AT thats super easy, someone else shifts from drive to reverse with a foot on the brake while you watch the engine with the hood open. MT it's a bit trickier, set the parking brake, slightly release the clutch but don't stall the motor. Or heel/toe the brakes/gas.

Inspect your driveline carrier bearing, it might be shot but not vibrating yet.

 

Your symptoms sound like engine mounts for sure. I had all the symptoms you had, additionally there was a jerk and slight rpm dip/jump on and off throttle as the engine twists.
It's all very subjective, my engine mounts didn't look that bad from the outside when I jacked up the engine slightly but then when I took it apart one of them was broken in half. If they're 13 years old, they've served their purpose and it's time to replace them, unless you want to drive like a granny everywhere to avoid blowing your old brittle mounts.

There are two engine mounts, and they're a nightmare to replace with the engine in the car. The procedure is straightforward like any car but access to the bolts is extremely limited and you either need specialized tools or a welder to modify a wrench to get at one of the bolts. Take a look at my recent thread for a couple pictures of what you have to deal with - I don't have a welder so I'm waiting for a 14mm torque wrench adapter to get that top mount bolt off.

 

At least our cars aren't like 7th gen Accords (I have one) and 3rd gen Acura TLs. Pretty much can count on engine mount failure every couple of years. They make the rubber soft to prevent vibration but soft rubber tears. Finally had to go with a urethane mount on the passenger side mount to rectify the problem. At least with RWD vehicles you generally only have two but access sucks. Not sure if there is a urethane option for our cars but might be worth a trade off of some vibration (mostly as idle with the a/c on) for greater durability,

 

I'm installing the Z1 poly engine mounts along with a rubber trans mount for NVH isolation. These shouldn't break. In fact, if I ever do I swap, I'm going to keep them.
To OP, you can try installing an engine damper kit or just brace your engine with tight cable ties or zipties in order to take stress of the mounts, my engine damper helped a LOT until the screw stripped out of the block and the completely blown mounts showed through...