1996 C3500 Crew Cab Dually

[RatPwrd72]

I've been chasing a rattling sound from the rear of the truck for awhile and finally found it. The factory muffler has started coming apart and making weird noises. Took it to a local shop in Saturday morning and got a Magnaflow PN#12588 installed. Installed it backwards (dual in/single out) and used the factory tailpipe. I did have him cut it off just over the rear axle for a cleaner look. Nice and quiet. This truck is meant to tow the loud stuff and I'm not a fan of listening to it on long trips. Looks like one of the factory cats needs to be replaced, I'm on the fence about replacing them both or taking them out altogether.

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[Jorge6.5]

I hear you on the cats. On my 454, one is clogged and the other is blowing out lol. Proper replacement is gonna be big bucks that I dont have. Removing them altogether would be an option, not sure what your laws are but here on my truck it is not required for emissions testing

Been thinking about going with a similar muffler. Do you have any video of the sound?

 

[RatPwrd72]

I hear you on the cats. On my 454, one is clogged and the other is blowing out lol. Proper replacement is gonna be big bucks that I dont have. Removing them altogether would be an option, not sure what your laws are but here on my truck it is not required for emissions testing

Been thinking about going with a similar muffler. Do you have any video of the sound?

We don't have any emissions testing or vehicle inspections in Oklahoma, so I could take them off with no problem.

I can try to shoot you a video, just imagine stock with some attitude. Can't hear it at all while idling or cruising normal and that's just how I wanted it.

 

[RatPwrd72]

I've been dealing with an intermittent CEL and the code stored shows EGR circuit short. I've checked connections, wires and fuses with no luck. Sometimes you can drive a week and it won't come on and then it's on when you start the truck. Frustrating. This issue and the fact that I have 1 cat that needs replaced has lead me to get a tune done on the ECM. I shipped it to BlackBear today and they're going to do a custom tune along with deleting the EGR and rear 02 sensors. I'll be headed back to the muffler shop and cutting both cats off. Not really looking to make a tire fryer out of it, but a few more MPG's wouldn't hurt a thing. The tune alone is the same cost as an EGR valve (nearly) and it won't have the opportunity to fail later on.

 

[Jorge6.5]

Eagerly waiting results.

 

[RatPwrd72]

BlackBear got the ECM tuned and shipped back to me without a hitch. It took about 3 minutes to install, might be the fastest mod yet and one of the most noticeable for sure. Once the new ECM was plugged up and the truck running, it sounded smoother already. I haven't had any issues with misfire codes or any fuel system related problems at all, but the tuned ECM made a difference right away. I opted for the firm shift points and they feel just right, not too harsh at all. Speed limiter is removed and tested... CEL for EGR is gone. Well worth the money. I've driven it about 150 miles since I put it in last week and it looks like I gained about 1.5 MPG average.

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[RatPwrd72]

My factory amber cab lights didn't look right after swapping the clear parking lenses and corners in awhile back, so I splurged for a $28 set of clear cab lights with LED bulbs. These don't light up the hood and roof like the stock ones did, but they do look a little cleaner, IMO.

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[Jorge6.5]

Did you have the cats deleted yet?

 

[RatPwrd72]

Did you have the cats deleted yet?

Yes, the cats are gone. I changed the ECM on friday night and removed the cats Saturday morning. I drove it with the cats still in and the new ECM installed. I could tell a difference on Saturday after they were cut off. One of mine was pretty much plugged off and the other was hollow. The engine seems much happier now.

 

[Christian Steffen]

Yes, the cats are gone. I changed the ECM on friday night and removed the cats Saturday morning. I drove it with the cats still in and the new ECM installed. I could tell a difference on Saturday after they were cut off. One of mine was pretty much plugged off and the other was hollow. The engine seems much happier now.

What do you think of the sound difference without the cats?