My kitchen sink was leaking under the cabinet, so I saw that the leak was probably from the basket strainer or the nuts and washers being too old.
I took it apart and this was the old setup
The nut on the tailpiece - the washer was rotted away. The basket strainer threads were all chewed up. So I decided to get everything replaced from the slip joint nut & washer up (shown by the pic here):
The blue arrow is the new slip joint nut and a new washer of course. Everything from there and up was replaced. Everything after, I left as is.
There are no leaks at all. However, when you operate the sink, it drains perfectly fine and fast until you overwhelm the basket with water for a while, then it backs up and the pool of water drains painfully slow like there's a blockage. Eventually it will fully drain and when there's no pool, then the drain operates just fine as water enters it.
The old setup did not have this problem at all. It drained just fine. This only started after I replaced things. That's why I don't suspect a clog, rather some issue with physics and the way I decided to replace everything.
The tailpiece is this from Home Depot:http://www.homedepot.com/p/Everbilt-1-5-in-x-8-1-2-in-Polypropylene-Hi-Line-Branch-Tailpiece-C9818/205153898
The slip joint nut and washer is this from Home Depot:http://www.homedepot.com/p/Everbilt-1-1-4-in-Plastic-Slip-Joint-Nut-and-Washer-C2798C/205153717
And the basket strainer, I got from a specialty plumbing store. I Googled it and found it here:http://www.jonesstephens.com/product/b02003/
Thanks in advance for your help fellas!