I suspect there is a quieter one too, but I forget what they are called (perhaps the "Hushpower" series). They have good descriptions of all of their mufflers on their website.

EDIT:
nope, the Hushpower II series are small limited space ones. You might try calling Summit racing and asking them, specifically about the 70 series. It is a larger muffler for Big Blocks, might have a stronger muffling effect than the 50 series. They look like they might be a little pricey though, like $170. The 50 Series SUV is only about $80 I think...

 

Cool thanks!

 

OK. Back to me

I fixed my rattling/vibrating muffler tonight!

I crawled under the truck and confirmed that it was indeed coming from the muffler itself. The muffler has an outer metal shell wrapped tightly around it, which is held on by 9 or so small tack welds. There is a very thin layer of insulation batting between the muffler itself and the muffler outer shell. As I was tapping the muffler (outer shell) with a rubber mallet, I shoved a long flat screwdriver between the two layers, and pried them apart a bit. The vibration sound decreased.

I then figured there must be a bit of dirt or loose rust between the two layers, and figured I had nothing to lose, so I might as well pull the outer shell off to see if I was right. A chisel and hammer made quick work of those little tack welds, and the outer shell came off no problem.

See picture of outer shell here.

Between the two layers, I found this. The pile on the left is the pieces of thin insulation that I removed. The pile on the right consists of dirt and pieces of loose rust - the source of the noise!

Now that the noise is gone, my muffler sits there with no outer shell (which I assume is only there for extra protection - to make the muffler stronger and to help slow down the rusting of the inner layer of the muffler.) I am considering cleaning off the muffler with a wire brush, buying a can of high heat paint, and giving the muffler a new rust resistant coating. Good idea? Bad idea? Not worth the trouble? Should I consider trying to re-install the outer shell on the muffler? (I'm not liking my odds of getting it on there as tight as it was before with a new layer of insulating material between the two.)

I appreciate the replies, guys. I guess the flowmaster 50 purchase and installation will be postponed to a later day.

 

Great work!
I guess that I may have to take a close look at mine. My outer shell is nearly rusted off.
Cheers ,
P

 

nice work getting up in there an investigating. If I were you I would probably try to treat the outer shell with a wire brush & high heat resistant paint then have it reinstalled. That outer shell may act as a rust protector AND heat protector.

 

I'd venture to say that any magnaflow muffler will probably be louder than stock when idling. Typically, the longer the muffler, the quieter it gets. From my experience (and this is on a Tacoma, not a 4runner keep in mind), the 18" magnaflow isn't really much louder than stock, but it's definitely louder than the 24". When I had it installed, they also held up the 24" and 14" magnaflows so I could hear what they sounded like. I couldn't tell a difference between the 24" and my stock muffler.