Cat Removal - Chevy and GMC Duramax Diesel Forum
11-16 LML Performance Parts Discussion Discussion of Performance Parts For the 2011 to 2016 LML Duramax Trucks No Advertising

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post #1 of 31 (permalink) Old 11-08-2019, 01:37 PM Thread Starter
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Cat Removal

My truck is deleted, but I left the cat on to keep it quiet and also for visual inspections, I put a muffler in place of the DPF so it isnít readily noticeable that itís been removed. After about 130,000 mile of being deleted my fuel mileage is starting to go down. My mechanic says my cat is probably full of soot since the DEF isnít being injected to keep the cat clean. Iíve got another cat thatís been cut in front (missing V-band), that Iím going to hollow out and swap out, but after looking under the truck the cat is sandwiched between the trans crossmember and the torsion bar connection/end piece.

How difficult is it to pull the trans crossmember and what do you use to support the trans? Can this be done without a lift?


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post #2 of 31 (permalink) Old 11-08-2019, 02:57 PM
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Quote:
Originally Posted by Thatmarkguy View Post
My truck is deleted, but I left the cat on to keep it quiet and also for visual inspections, I put a muffler in place of the DPF so it isnít readily noticeable that itís been removed. After about 130,000 mile of being deleted my fuel mileage is starting to go down. My mechanic says my cat is probably full of soot since the DEF isnít being injected to keep the cat clean. Iíve got another cat thatís been cut in front (missing V-band), that Iím going to hollow out and swap out, but after looking under the truck the cat is sandwiched between the trans crossmember and the torsion bar connection/end piece.

How difficult is it to pull the trans crossmember and what do you use to support the trans? Can this be done without a lift?


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the DEF is a reactant to reduce emissions, as far as i am aware it has no bearing on soot buildup in the cat. If your mechanic were correct, all the trucks built before 07 would have clogged up cats every few years. Thats not to say that your cat isnt the issue, it might be, but not because of the DEF.

As for removal, a lift would make life easier but you can do it on jack stands, get a block of wood and a jack to support the transmission, or cut the exhaust so you can remove the cat without taking the cross member out. This is how most i know have done it when adding aftermarket exhaust, not sure how that would impact your semi stock setup though.

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post #3 of 31 (permalink) Old 11-09-2019, 05:26 PM
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what muffler did you use instead of a DPF delete pipe? Got any sounds clips?

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post #4 of 31 (permalink) Old 11-10-2019, 02:59 PM
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what muffler did you use instead of a DPF delete pipe? Got any sounds clips?
His signature shows what muffler he uses.
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post #5 of 31 (permalink) Old 11-10-2019, 03:10 PM
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Quote:
Originally Posted by Thatmarkguy View Post
My truck is deleted, but I left the cat on to keep it quiet and also for visual inspections, I put a muffler in place of the DPF so it isn’t readily noticeable that it’s been removed. After about 130,000 mile of being deleted my fuel mileage is starting to go down. My mechanic says my cat is probably full of soot since the DEF isn’t being injected to keep the cat clean. I’ve got another cat that’s been cut in front (missing V-band), that I’m going to hollow out and swap out, but after looking under the truck the cat is sandwiched between the trans crossmember and the torsion bar connection/end piece.

How difficult is it to pull the trans crossmember and what do you use to support the trans? Can this be done without a lift?


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Not having the DEF clogging up the cat is a good thing, having only soot is easier to burn off.
You show Motor Ops for tuning do you have the AutoCal where you can do a data log and email them the results.
What’s your balance rates show ?
Are you using any diesel additives, the fuel quality is going downhill?
Are you using bio fuel to high of a % will affect mileage.

What kinda fuel mileage drop are you experiencing?
Weather changes affects mileage.

Drive the front on blocks, 6” would work.
Unbolt the crossmember and slide it out of the way.
Floor jack to support the trans.

Having personal experiences with cat and without cat, without, it’ll be a little louder and mucho diesel exhaust stink that even a aftermarket cat can not handle.

I put mine back on after 5 years of suffering with the stink.
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Dan
2007.5 GMC Sierra 3500 SRW L.B."BLACK" C.C. 4X4 LMM Z71
DIY stock airbox mod, aFe ProGuard 7, OEM drop-in
EFILive ECM ATP - Heavy Tow Tune with Turbo Brake.
EFILive TCM Duramax Tuner
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DHD PCV Re-Route
AirDog 4G100

2007 Yukon Denail "BLACK" 6.2 gasser
DIY stock AirBox Mod, K&N, Airaid intake, EFILive TCM only tuning

Last edited by D_R_C; 11-10-2019 at 03:16 PM.
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post #6 of 31 (permalink) Old 11-10-2019, 04:28 PM
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I'm sorry, I didn't hear your question. I was distracted by your wonderful Avitar.
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post #7 of 31 (permalink) Old 11-12-2019, 09:02 PM Thread Starter
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Quote:
Originally Posted by Caleb 6R View Post
what muffler did you use instead of a DPF delete pipe? Got any sounds clips?


I tried to add a video, but there is no video upload on Tapatalk or the mobile website.
Thereís a little rumble from 1100-1300 rpm, but thatís all you hear from the inside. On the outside it has a slightly deeper tone, but not much. Itís not any louder than stock on the inside as the engine makes so much noise to begin with.




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post #8 of 31 (permalink) Old 11-12-2019, 09:14 PM Thread Starter
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Quote:
Originally Posted by D_R_C View Post
Not having the DEF clogging up the cat is a good thing, having only soot is easier to burn off.
You show Motor Ops for tuning do you have the AutoCal where you can do a data log and email them the results.
Whatís your balance rates show ?
Are you using any diesel additives, the fuel quality is going downhill?
Are you using bio fuel to high of a % will affect mileage.

What kinda fuel mileage drop are you experiencing?
Weather changes affects mileage.

Drive the front on blocks, 6Ē would work.
Unbolt the crossmember and slide it out of the way.
Floor jack to support the trans.

Having personal experiences with cat and without cat, without, itíll be a little louder and mucho diesel exhaust stink that even a aftermarket cat can not handle.

I put mine back on after 5 years of suffering with the stink.


I havenít run a data log yet.

My balance rates are all been -1.5 to +2.2. I have one injector which is at about +2.8.

I run OptiLube XPD at each tank (1 oz. to 4 gallons). We donít have any biofuel places out here.

On long runs about 100 miles Iíll get about 16.5-17 mpg running about 80mph. Now Iím getting about 14.5 on a 35 mile run back and forth to work now. When I first deleted I was getting around 19mpg at 80mph.

Iím in SoCal so we really donít have much of temperature changes.


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2011 Chevrolet Silverado 2500 HD LTZ Crewcab Duramax/Allison
DPF Delete, MotorOps Tuning, Corsa Muffler
5000K HID Light Kit, Fass 150 Lift Pump
305/55/20 Cooper Zeon LTZ
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post #9 of 31 (permalink) Old 11-12-2019, 09:17 PM Thread Starter
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I'm sorry, I didn't hear your question. I was distracted by your wonderful Avitar.


Believe it or not someone PMíd me saying it was offensive to them and wanted me to change it.
What a h**o.


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2011 Chevrolet Silverado 2500 HD LTZ Crewcab Duramax/Allison
DPF Delete, MotorOps Tuning, Corsa Muffler
5000K HID Light Kit, Fass 150 Lift Pump
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post #10 of 31 (permalink) Old 11-12-2019, 09:51 PM
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Quote:
Originally Posted by Thatmarkguy View Post
Believe it or not someone PMíd me saying it was offensive to them and wanted me to change it.
What a h**o.


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I wouldnít mind if you changed it.

You could take her shirt off.

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