So, I had the shop remove the old system and replace the new piping (3" - stock) and run it into a Series 70 Flowmaster. Basically the same exact spec in terms of bends, etc but with the Flowmaster...

Sounds great at idle, but when you take off, you get a droney sound. My wife and son were following and he said it sounds like a fart can on a Civic. The biggest issue however, is at freeway speed...

At 55-60 MPH, the drone is so bad that I am seriously worried I made a mistake. It is really bad.

I called Flowmaster and asked them and they stated that V10s do have that sound, but the drone could be from the computer learning everything since I added the muffler. He said to give it a couple of hundred miles and then see how it does.

I have had 7.3s and if you put the muffler on the correct way, it has all the sound exit the tailpipe. If you put it on backwards, you will get a drone in the cabin.

Is it possible they put it on backwards?? I know they had a bright orange decal on the inlet end. Is there a way to check and see if it is correct by an embossed arrow or similar?

Do I need to get a resonator and put it before or after the muffler...

 

I don't forsee the truck "learning" and getting rid of the drone.

Any aftermarket intake, y-pipe, headers and etc? Is the new pipe mandrel bent or typical exhaust shop crushed bends? What rpm is the drone at?

Anyway the Flowmaster 70BB2 is directional so it has to be installed properly. Below is a pic of the inlet and it should be stamped "inlet" on the case end.

 

Mine was droney to with stock manifolds and a SPD Y pipe. I installed Banks headers and Y pipe and it is MUCH better.

 

It might have the cat removed and the tubing is all mandrel bent.

Muffler is in about the same location as the OEM was in terms of distance back from the spot where the three bolts are. They welded everything and the only thing different from stock is they angle cut the tip. The piping is all 3" also...

I am not sure as to the RPMs as it is a van w/o a tach. Again, at 55-60 it is killer loud and from a dead stop, initial acceleration causes it to "braaaaap" and then fades to a nice growl.

I gotta go out and look to see if it is on backwards.

 

So, it is on correct. Inlet is facing towards the engine bay! Had to go out tonight and check or I wouldn't have been able to sleep!

 

I had an Original 40 on mine, was horrible with drone. I know the 70 is supposed to be better, but it's still a chambered muffler. Plus the body of a van is like a big drum.

I put a Dynomax VT on, no drone now.

 

I know that I'd have to buy another muffler and then it is still a gamble in my mind. I was told the Series 70 was the right one and it drones like mad.

If I buy a VT, that's another $100. Plus labor to cut off and re-install.

Anyone doing a resonator? Just seems to be counter productive, though...

 

VT n 3 inch piping, with a 3.5 inch tip, thats it. My exhaust shop was nice enough to swap mufflers simply for the difference in cost between the 2, glad I paid the extra $120.

 

The problem is the lack of a cat - stuff a live cat in the pipe and it won't drone anymore

But seriously, without the cat, all I've ever heard from people with V10s is that the noise is unsavory.

A completely different setup, but on my '74 highboy that didn't need a cat, I had separate duals with thrush mufflers on it - drone. I added another muffler right after the first one on both sides, and the drone was gone.

I think some sort of resonator where the old cat was would help a lot.

 

I've heard on multiple occasions people complain about the noise without a cat... Now, my mustang is loud enough to wake the dead, so loud is going to be relative. I have read about a few who have put a glasspack straight thru muffler in place of the cat; which got rid of the drone. They're not all that pricey and would be worth a shot IMO. They're definitely not gonna flow any worse than that huge cat.

 

Then you might have identified the root cause!

Cats actually quiet the engine down quite a bit while eliminating the stink. And if large enough (like stocker), at almost 0 impact to tq, hp, or mpg.

 

Every Flow-Master I've ever dealt with had an annoying drone.

 

I cant even hear my 50 series SUV in the cab, but its really loud outside...

 

Update:

We put on a resonator. Helped a good bit, but there is still a drone... I am pretty pissed that I bought this muffler, had to add a resonator and still have that fart can sound. I should have bought the VT muffler instead it appears. I should have left everything stock and just been done with it.

Maybe it will get better as we go... The shop thought we could run a Cherry Bomb vs the resonator, but felt it would be louder...

 

I also think the older V10s sound different as i went through a bunch of YouTube vids and everything sounded good. I didn't connect the dots that my old V10 and their newer V10s could sound different...