Hmm, how do I get the pics to show?

 

You have to copy and paste the image url (from right clicking your image) into the insert image dialogue. They come up fine when you click the links. In my opinion, that last glasspack probably isn't doing much to quiet things down at all. It looks like you put a lot of time into it, so its a shame it still isn't right.

If i were in your position, I would try:

1. Ending the pipes after the first pair of mufflers, and then if you like that, running those two out the side

or

2. Putting a "turbo" or chambered style muffler on it in place of your third muffler.

 

i am wondering what that big thing on the tail pipe is? might be part of your issue

 

That's the 4" glasspack.

Drone happens when your exhaust resonates at a frequently used rpm. Lengthening or shortening the tailpipe can help, as well as changing where the y-pipe meets. You can also try changing the pipe diameter. A chambered muffler is designed to reduce drone, so that could help as well. You could try adding a side branch resonator as well: basically a section of pipe that shoots off the main body of the exhaust that is plugged, and acts to cancel certain frequencies. You'll have to play around with the length to find what works.

What are your hangers like? Good rubber insulators are needed to make sure the exhaust doesn't resonate the frame. Also, make sure you are hanging everything on the frame, and not the body mounts or the cab.

Lots of good tech here http://www.chevelles.com/forums/showthread.php?t=356726

And lots of science I don't understand here http://crgis.ndc.nasa.gov/crgis/imag...f_Mufflers.pdf