By the way, I did a ton of research on this, as it seems to be a very very common problem for 350/370Z and G35/G37 drivers.
The rear liquid filled bushing wears out and eventually pops and leaks. Guess what? Nissan is happy to sell you the entire REAR SUBFRAME carrier to fix the problem for one stupid bushing. Yes, you read that right. They dont sell the bushing individually.
Good news is whiteline makes a bushing for G37/370Z's, and it Fits our cars. I picked up the bushings for about 80 bucks on Amazon.
Bad news is it requires the removal of the differential to repair it. If you know what you're doing, you can DIY, or find a Nissan specialist in your area to do the work.
The specialist I spoke to said on auto trans cars and less agressive driving, the bushing likely doesnt need to be replaced. I am going to go ahead do mine, I dont even want the thought of a leaky pinion seal... I got quoted about 350 for labor.
So FYI if anyone sees stuff leaking out the back of their EX, this is what it is.