It is time to upgrade the diff, but I just bought a new car for the wife to be. So I need to hold off on modding the Z for awhile.
The smell is still pretty strong still (still stinks up the garage but took an hour instead of 15 mins). A buddy told me that I should find the Vent tube that comes out of the diff, follow it till the end, and find the residue from the vented tube. Supposedly when the diff gets overheated, it goes out of this vent tube at the top of the diff cover and kinda goes into an open space in the left rear section of the subframe next to the rear diff bushing. (which explains why when I smelled the bottom of diff case, it's not very strong, rather it's all over the place).
Wish me the best of luck, still gotta fix it myself. Turns out the mechanic didn't really do much for me. $ down the drain.