Still have vibration/resonance. Wanna test running exhaust out. Flex hose?

it very well can be the exhast.
it still could be the motor and trans dont point down the center of the car. its very hard to figure out as it said earlyer.
when you floor it, the u-joints try to force them selves into phase if they are out of phase, when you cruseing they dont have the power to pull the driveline into phase. i dont know if this is your problem but dont what you do discount it.
do try the exhast first and if that doesnt do then consider my sugestion.
have you had a 4wheel computer alignment? if so it should have the rear thrust angle. that should be 0. if its not then the rear is not straight in the car and that could cause the problem.
i truely hope its just the exhast as thats the easiest to fix.

 

So thrust angle is what you are talking about, or is there also just the chance the engine is mounted un-square to the rear? Two different issues?

 

http://www.moparmagazine.com/2009/july_august/where_is_the_nvh.html

CHECK OUT THIS LINK SCOOPER. ITS A RUN DOWN ON THE COURSES WE DO FOR NVH. WONT DO YOU MUCH GOOD WITHOUT THE TOOLS OBVIOUSLY BUT ITS COOL HOW ONE CAN DIAG THESE ISSUES.

You can use this little tool(syrometer) for about 20 bucks and figure out vibes with math. It works great.
It was used by Briggs and Stratton as a tachometer. Ingenious little tool. When mounted you turn the dial until the wire starts to vibrate. The frequency on the dial is your NVH issue. If you suspect exhaust you can figure out the frequency for V8 exhaust and if it matches the tool reading you nailed it. (in a perfect world)LOL.
I know its pretty involved but it does work once you figure it out.

 

That looks like a fun little tool! I could get myself into all kinds of trouble with that!

 

I have a block of wood for a head. I'm still thinking it's a rear wheel axle flange/bearing. That's only because it was my problem and the descriptions fit.

 

I checked those pretty early on. When i took the rear out to have crush sleeve professionally crushed. Bearings looked fine.

 

Hmmm i wanna see the outcome on this one. I ran my exhaust the same way with my flowmasters and i never had a resonance or even a drone. I did have a similar vibration though, but i think mine is because of all my worn mounts. But i wont know till the new engine is in.

 

That is what I thought, too. Swapped out all mounts, trans and engine, and tailshaft housing, and tailshaft bushing, first thing.

 

scott mine has that same sound and my exhaust goes all the way out the rear.

 

So, what is this that so many of us are hearing/feeling?

Apparently not anything dangerous that will wear anything out, or we would all have dead cars (or soon would).

Do those of us who hear it all have sub-frame connectors? I wonder if it has something to do with the harmonic resonance frequency of the frame vs the v8 vibration resonance.

 

Neither of mine had sub frame connectors. Tail pipes got rid of about 80% of it on my last car.

 

Interesting. You say that tailpipes got rid of only 80% of it. So now I am really interested in where that last 20% comes from???

I have actually gotten rid of 80% of mine already, by zeroing out the pinion angle, and balancing and straightening everything out. But there is that last little bit that makes the car just not quite perfectly comfortable to drive. It would be a nice and quiet ride if it wasn't for that (outside of the exhaust note, of course! ).

 

try puting in a h-pipe. do some internet research on how to correctly locate and size the h-pipe. it involves locateing the point where the exhast gasses stall out in the exhast pipe. also there is something about using a pipe 1/2 the size of the exhast pipes. i did it once a few years ago and did feel a seat of the pants increase and a definte change in the exhast sound.