sounds to me like there's no real vent, and you are proposing only an AAV and the (so-called) wet venting.

is this reading correct?

yes , that's my plan. will it work reliably?

no. it will not work.

2/ where in your entire house are the real vents?

3/ you will need master plumber input.

the main 4" c.i. line i'm tying into has a vent stack about 18' upstream & services a toilet on the first floor.

The critical distance is the 15' one.

The fact that "the main 4" c.i. line i'm tying into has a vent stack about 18' upstream..." was the one thing you should not have mentioned in your first post, as it is irrelevant and only serves to show how little you know. No offense. I read and re-read your first post many times. It is a bit dense and it takes a while to figure out.

Repeating your "18ft distance" information in another post confirms my hunch and my reading of your situation, and it shows how little you have learned. Go learn and come back. Or, hire a Master Plumber. Or, stop asking if you can do it the way you asked in your first post.

If you post at other plumbing sites you may want to rewrite the first post completely. Please accept this information and advice in the spirit in which it was given. I'm not a plumber; feel free to post again, with new news or to ask for more input from more people.

Hth

thank you for your comments. i should have mentioned that the 3" line i'm re-routing serves a toilet on the first floor and is on a vented stack. so, i have a vented stack at the head of the 3" line and at the head of the 4" main line. does this clarify the drainage issue in the 3"? also have a drawing which might help: http://img204.imageshack.us/img204/3642/basei.jpg

thank you