Now you have me thinking about getting the 22 instead of the 18 ...a want the rumble, but not the drone on the highway. To bad they don't make a ...

Now you have me thinking about getting the 22" instead of the 18"...a want the rumble, but not the drone on the highway. To bad they don't make a 20"!!!

I did find the part number for a 22" single in/out 3" inlet/outlet, #12589. A I also found a couple of videos of this muffler on a newer GM truck...

Outside of cab

http://www.youtube.com/watch?v=c7CUE1qnO8c

Inside of cab

http://www.youtube.com/watch?v=ghPaCwbjIZ4

Those don't sound like a 5.3 to me................hmmm

gmctruckguy wrote:Had the 12259 in my '10, it got louder with time, was almost to loud for this old guy. I have the 22" in my '09 and '12 (3.5" exhaust) and it is a bit louder than stock and has a nice growl to it.

+1 on the Magnaflow 22". That's what I have on my 2003, part # 14590. As gmctruckguy said, it's gotten a bit louder but nowhere near unbearable. I took my dad for a ride in my Silverado right after I put the exhaust system on; we're running down the street with the windows down and he says "sounds like a Corvette". Oh brother!

I just ordered the Magnaflow 12586 from Newegg of all places...they had it for under $100.00. Should be here later this week and I'll have the shop install it Saturday. To keep the drone down in the ext cab, would placement of the muffler have any effect? Should I have them install the extention pipe before the muffler, moving it it back, then attach the tail pipe?

I installed a Magnaflow 12289 30" overall, 24" muffler today. Friend has 12259 24" overall, 18" muffler, but its too loud for my taste for interstate travel. Both mufflers fit 2009 GMC/Chev 1500's with 5.3L engine. I love the deep mellow sound of the 12289, and not loud doing 70-75 mph. Good Luck

Thanks for the info. I just got the Magnaflow 12586 in today and will have it installed this Saturday. I think I did good getting the 22" instead of the 18. I want the rumble at idle and at acceleration but not the constant drone on the highway.

I just had the muffler installed today and it sounds good. It is quiet at idle, just a little rumble, with the same at just cruising. Give it some gas and it makes a low pitch growl. It does get a little noisy in the cab at highway speeds between 1600-2000 rpm, but not bad. With the cruise control it does tame it a little. One thing I have noticed is the throttle response has improved at takeoff. I will check mileage after a few tanks to see if it improves...if I can keep my foot off the accelerator.

I've had it about a week and really like what this muffler offers...it sounds great when I want it to, improved throttle response, and for this week I have noticed a little gain in mpg. I know it will improve over time.