Which muffler is a direct replacement?

Shaners · July 29, 2003

I'm considering a replacement muffler for my stock "can" to compliment my new PCM that I ordered from Westers Garage.

I just want to add the muffler in the place of the stock dual-in/dual-out muffler. I see that Magnaflow (part # 12599) looks like it may work, but I'm not familiar with the sound of it. I don't really want anything louder than the 70 series Flowmaster, but the Flowmaster in the correct set-up is only a 2.5" dual/dual as compared to the Magnaflow 3" dual/dual, which I think would be the correct fit...

Any thoughts as to the sound of the Magnaflow? I only want it to be slightly louder than stock, and no drone or resonance in the cab... I know the 70 Series Flowmaster would fit the bill for the noise, but then again I don't want to restrict my exhaust to 2.5" pipes...

katie-bug · July 30, 2003

Shaners,

I have a magnaflow muffler "spliced" into stock exhaust system. It is dual in/single out re using stock piping, 2 1/4 inch dual in and 3 inch single out, I believe. Rig is an '01 2500HD 4x4 with the 8.1L and Allison transmission.

Slightly louder than stock. Resonance in cab around 2,000 rpm, but not excessive. Wide open throttle sounds like a big block, but not excessive. Elsewhere in rpm band slightly louder than stock with lower frequencies emphasized. I like it. There are no baffles, etc, inside this muffler, only steel wool like packing around straight through portion. I wonder why it is not a lot louder than it is, looking at it's construction.

Am contemplating magnaflow dual in/dual out, again re using stock piping back to mufler inlet and I beleive dual 3 inch out.

Prior to leaving for Saudi Arabia next month will add Skyjacker 6 inch suspension lift with 5 inch lift rear leaf spring (no block), Weld Cheyenne wheels and LT 285 or 305 All Terrain T/A KOs.

Richard

2001 HD · July 30, 2003

Hey Shaners-Take a look at Flowmaster's website. They have a new "50" series muffler in the "Whats New" section designed especially for the 6.0 and I think 8.1. Dual 3" in Dual 2.5" out which should help with less low end torque loss in a dual setup. I've been looking at these, but like you I would like to see it in a quieter "70" series.

1BADHD · July 30, 2003

I have the Flowmaster direct swap. I beleive its a 2.75 dual inlet and dual 2.5 outlet. Love it!

ShortCrew · July 30, 2003

I have a spliced a Magnaflow on my truck. Dual 3" in, single 4" out. I used a 4" to 3.5" reduce and a 3.5" mandrel ubend to connect it to the stock tailpipe.

The sound is very mellow and very quiet. No droning in the cab at all. I was actually quite surprised at how quiet it is since the muffler is straight through.

for Magnaflow

JimWilson · July 31, 2003

The Magnaflows I've heard have a nice sound, but can't say if they drone in the cab because I was listening from outside.

Be careful of using 3" pipes. If you lose too much backpressure you'll also lose some of that new-found Westers oomph. The 6.0 still needs some backpressure to get lowend torque.

1BADHD · July 31, 2003

If you go dual in/out......big pipe is OK. But...if you go to true duals a 2.5" pipe or less is all you will need. I had true duals with 2.5" pipe. Went to dual in/out muffler and 3" piping. What a difference. I got all my lost low end back. Maybe a little extra!

bowtiepatroit · August 4, 2003

Check out flowmasters big block 50. Good choice for these truck mine seems to like it. What I have noticed with mine so far is lower op temps, a tad it better twoing power(pulling about 8500# of 5th wheel). Not sure on MPG can't seem to get no better than 8.5 to 9 with this rig.