Civilian pn for muffler gasket M939? Or other way to seal?

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LCA078

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I'm replacing my muffler on the M923 with NHC250 (I think same muffler regardless of engine?). It's the typical rusted out around the bottom and a safety hazard. Anyone know a civilian part number for the gaskets? Or a way to use some other sealer besides the OEM gasket?
 

LCA078

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Aaahhh- that's explains why I didn't find much on my search as I was using 'muffler gasket' versus 'exhaust gasket'. Thanks for the link! Memphis only shows one gasket for bottom side that connects with the flex hose. Is there also one on top?

And since I have two trucks who need mufflers, I was hoping to find a cheaper solution at Napa, O'Reilly's, etc. so any cheaper alternatives would be great.
 

TheQuaker

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YMMV but I replaced my M923's muffler last summer (same issue rusted out bottom and getting fumes into the cab) and used the factory replacement gaskets. Perfect fit, no issues.

My personal time and frustration running around looking for a suitable replacement at a truck parts place is worth more than the amount I would have saved finding a non-OEM replacement, in my opinion. Without a Cummins/Cat/Freightliner/Donaldson, etc. part number to cross-reference forget it. The counter kids at most of the parts places near me have no clue how to help you without a part code to punch in to their computer.

And yes, there is a second gasket at the top connecting the muffler to the stack.

In my case the top gasket on mine was not so bad and I could have reused it but the bottom one was toast. Since I had pre-ordered everything to complete the job I replaced both gaskets with new. No regrets.
 

charlesmann

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iv got the same issue, rusted out, blowing hot exhaust directly onto the fuel tank. i was thinking of just removing and replacing with a straight pipe. any down side to straight piping on a A2series, other than noise?
 

simp5782

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There is no civilian equal for the muffler gasket. Upper and lower gasket are the same. Made by Bosch Rexroth # 12255817
 

LCA078

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Charlesmann- You could to mount the upper elbow on the up-pipe like a muffler delete in a tempary fashion just to see what the sound is like. But I'm also sure your A2 will sound much different than my old school M923.

Wes- If you say there is no alternative, there is NO alternative. Thanks
 

charlesmann

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Charlesmann- You could to mount the upper elbow on the up-pipe like a muffler delete in a tempary fashion just to see what the sound is like. But I'm also sure your A2 will sound much different than my old school M923.

Wes- If you say there is no alternative, there is NO alternative. Thanks
different meaning better, or different meaning like a ford or chevy straight pipe turbo back compared to a cummins turbo back?

i was looking at mufflers too, and them dang things high dollar, $375ish. then there is shipping on the oversized exhaust garbage can.
cold a civi diesel muffle work with a lil modding of the trucks muffler support structure? viable option?
 

simp5782

My safe word is Pork and Beans.
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different meaning better, or different meaning like a ford or chevy straight pipe turbo back compared to a cummins turbo back?

i was looking at mufflers too, and them dang things high dollar, $375ish. then there is shipping on the oversized exhaust garbage can.
cold a civi diesel muffle work with a lil modding of the trucks muffler support structure? viable option?
 

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charlesmann

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I would say a very viable option.
i haven't measured pipe size yet, and I'm on a 3.5 work hitch in canada, so measuring right now is out of the question. but what size pipe is the exhaust system? looks like 4". i can't remember where on here, but i remember someone saying the smaller pipe cause more restriction, which also is a mpg and power limiting factor compared to the civilian trucks.

would increasing to say a 5 or 6" turbo back help with mpg (not really worried, but 8-10 mpg is better than 3-5 mpg) but more so a bit more power? I'm looking at, and i hate to say it, cheap, performance upgrades. a charge air cooler is completely out of the cost question right now. playing with ip might be something i look at in the future, but not in the next few (4-6) months.

i know the more and colder air an eng can breathe, the better it performs, but it must be abe to exhaust that same amount or more of air.
 

simp5782

My safe word is Pork and Beans.
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I would say a very viable option.
i haven't measured pipe size yet, and I'm on a 3.5 work hitch in canada, so measuring right now is out of the question. but what size pipe is the exhaust system? looks like 4". i can't remember where on here, but i remember someone saying the smaller pipe cause more restriction, which also is a mpg and power limiting factor compared to the civilian trucks.

would increasing to say a 5 or 6" turbo back help with mpg (not really worried, but 8-10 mpg is better than 3-5 mpg) but more so a bit more power? I'm looking at, and i hate to say it, cheap, performance upgrades. a charge air cooler is completely out of the cost question right now. playing with ip might be something i look at in the future, but not in the next few (4-6) months.

i know the more and colder air an eng can breathe, the better it performs, but it must be abe to exhaust that same amount or more of air.
4in is plenty for the wimpy h1e turbo the 8.3 has. Upgrade to an hx40 for more air and power. 4in will still be fine

@Csm Davis has a straight up pipe setup in his wrecker. Maybe he will chime in
 

Floridianson

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different meaning better, or different meaning like a ford or chevy straight pipe turbo back compared to a cummins turbo back?

i was looking at mufflers too, and them dang things high dollar, $375ish. then there is shipping on the oversized exhaust garbage can.
cold a civi diesel muffle work with a lil modding of the trucks muffler support structure? viable option?
Look in our classifieds? When I did mine the gaskets were trashed but the way the pipe fits together and clamps I did not use a gasket and it did not leak.
 
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LCA078

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Second on the above. Supporting our own is a good thing.

On the flip side, I purchased two new M939 mufflers off Ebay for $90 each shipped to the front door in 3 days.
 
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