Let me know how yours was installed. If it's the same as mine and others are opposite, that may be a big part of it.

 

Holy huge pipe.... sure that wasn't meant for a diesel? lol

 

No kidding... They told me that they recently switched to 3" as of Dec 10th. I imagine the smaller diameter may also help keep the drone down from other things I've read.

 

Well I looked at my muffler and nowhere does it say MBRP on it. I'm very sure its back wards though. I'm going to take it apart and look inside. The drone can be the 3.5 inch pipe before the muffler. Or the exhaust is not flowing with the louvers (normal) but against them causing air disturbance drone (back wards).

 

the drone on mine isnt bad. when cruising at 70-75 down the highway i can barely hear it. With the radio is turned up like 4 bars i cant hear it. my truck runs at about 2100 rpms at 75.

And who ever it was that said 3 1/2 is huge wasnt joking!! i pulled it out of the box and was shocked then the tip was a 4 incher!!

 

Cured my drone!

 

Do you know what was installed on yours?

 

When I bought the truck August 09 it had a SI/DO Flowmaster catback with a lote of drone. I added a 28" long Thrush Glasspack # 24214 in front of it to act as a resonator. I posted a thread about it and in this one below.

https://www.f150online.com/forums/ex...rone-help.html

 

Thanks tbear 853. That's the thread that made me consider adding the Thrush as a resonator.

MBRP is closed today. I think I'll call them in the morning before I have the Thrush added, to see if the muffler should be cut to have the ends swapped to flow the other direction also.

 

I had the Thrush glasspack installed in front of the muffler today. The MBRP muffler does appear to be non-directional as it appears to be the same no matter which end faces the front or rear. The open end of the raised dimples in the muffler face both the inlet and outlet, changing the direction of the open end of the dimples in the middle of the muffler.

The drone, and muffler tone, are reduced. The drone is not gone completely, but it is much less. Liveable. I may mess around and try adding weight to the muffler somehow, seeing if I can reduce the drone further. Perhaps a piece of steel that has the same curve as the muffler, and use some header tape to cushion the steel plate. I don't know if anyone has tried this, but out of curiosity I'd like to see if it is the muffler resonating, the tailpipe, or whatever.

Perhaps the sounds and drone may change a bit as I get some hours on the glasspack.

I did use a Thrush which has a perforated core. I know there are some glasspacks that have the raised dimples with one end of the dimple open. I assume these would change the sound and tone differently than the perforated core glasspacks, but I don't now for sure.

BTW: the surface rust on the mid-pipe and muffler is after 2 weeks in our Wisconsin winter. This is the 409 stainless.

Muffler inside:

[IMG][/IMG]


Before:

[IMG][/IMG]

After:
[IMG][/IMG]

 

The 3 1/2 inch pipe before the muffler is where I thought the drone was mostly coming from. I bolted 3/4 inch solid bar to mine and it did cut the drone down to the 1800 rpm mark. I'm going to try factory pipe just before the muffler and see what happens.

*** Thanks for the follow up! Thanks to Tbear as well I might go this route as well.

 

To powerz69 - The pipe in front of the muffler could be where some of the drone was coming from. Adding the smaller diameter glasspack cut a good part of the drone down. The Y-tube is just in front of the connection to the mid-pipe, and dumping 2.5" O.D. exhaust gasses right into the 3.5" O.D. pipe could have been contributing to the drone.

I'm thinking the drone that is left may be coming from the muffler. I say this because at one time, I had a magnaflow universal straight thru muffler on this truck, similar to the shape of the MBRP. With everything else stock except the muffler, I had drone similar to the drone that is left in the current MBRP setup. That's why I was wondering if anyone has ever attached weights to the muffler itself, to see if the additional weights, in the right spot, may soften the drone (i.e. 4 smaill weights spaced around the muffler in the middle of the muffler may cut the available resonating difference in half?). I'm just not sure how to best try this. If it did work, I imagine a guy could just JB weld the small weights to the muffler casing.

 

Or clamp weights using stainless hose clamps.

Factory used weights on the intermediate pipe on my '07 for some reason and my '01 Merc
had weights mounted to both sides at the connection point where the flanges are between
cats and mufflers where my police cars never had weights. Merc had two resonators too.

Glad the front additional glasspack seemed to help. That 3 1/2 inch pipe was adapted after
the two front head pipes from the cats came to a Y and left the Y with 2 1/2" so I doubt
you hurt yourself any with the new glasspack.