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Old 03-03-2018, 10:56 AM   #1
manimal
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Lets talk Catalytic Converter positions

On my 94 Suburban 2500 7.4, 2wd, my cat is AFTER the muffler just before rear axle. It looks fairly new, but my smog test, I just squeaked by by points of failing on 1 part(i will have to look which one).
I thought a cat needed to get HOT to be efficient? If I put in closer to the front, where does it go?
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Old 03-03-2018, 10:58 AM   #2
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Re: Lets talk Catalytic Converter positions

It should be ahead of the muffler. I'm surprised it passed, as strict as they are. They are staggered on the pass side, under the foot board/seat.
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Old 03-03-2018, 11:19 AM   #3
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Re: Lets talk Catalytic Converter positions

Mine is a single(94). the y-pipe is stock and has not been cut. I have seen a couple others this way, but I dont understand the reasoning behind it. I plan on moving it forward, but need to see pics of stock locations.
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Old 03-03-2018, 02:08 PM   #4
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Re: Lets talk Catalytic Converter positions

No oem cat has ever been installed after a muffler, period.
I have the oem service manual, all 4 books and like 3000 pages worth.
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Old 03-03-2018, 04:42 PM   #5
95 S_Trucker
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Re: Lets talk Catalytic Converter positions

Every 92-95 3/4 ton suburban that I have worked on had the cat at the rear behind the muffler.
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Old 03-03-2018, 05:14 PM   #6
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Re: Lets talk Catalytic Converter positions

Is there a reason they are behind the muffler? Can they be put in FRONT like all the others? Or is something in the way or what? I looked under mine and dont see any reason it cant be moved, but GM did this for a reason that I dont understand.
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Old 03-03-2018, 05:41 PM   #7
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Re: Lets talk Catalytic Converter positions

Quote:
Originally Posted by 95 S_Trucker View Post
Every 92-95 3/4 ton suburban that I have worked on had the cat at the rear behind the muffler.
That really defies logic since a cat has to reach a certain temperature before it will even work. The only unit I'm aware of installed after a muffler is a resonator.
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Old 03-03-2018, 06:11 PM   #8
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Re: Lets talk Catalytic Converter positions

I'll get some pics of my walker catalog when I'm at work on Monday.

I should have clarified earlier, the only ones I work on are big blocks. Small blocks may be different.
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Old 03-03-2018, 09:31 PM   #9
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Re: Lets talk Catalytic Converter positions

My '89 K3500 Single cab/single rear wheels has the cat behind the exhaust near rear axle
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Old 03-04-2018, 08:33 AM   #10
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Re: Lets talk Catalytic Converter positions

I had 2 454 1 tons 88 and 89, both were in same location, under pass side, before muffler. something doesn't make any sense.....
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Old 03-04-2018, 08:09 PM   #11
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Re: Lets talk Catalytic Converter positions

My original Cat is stuck above the transmission cross bar & has a "32 of an inch of room, above / below. I need to change it & move it past the tranny support.

It actually rests on the support... ( exhaust is kinda old)
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Old 03-04-2018, 11:34 PM   #12
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Re: Lets talk Catalytic Converter positions

Couldn't find the Suburban, but the 3500 checks out. Converter behind the muffler.
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Old 03-04-2018, 11:50 PM   #13
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Re: Lets talk Catalytic Converter positions

I just dont understand why though. Its my understanding the cat needs to get to a certain temp to operate correctly. Why did they only do this for a couple years and then go back to the forward position?
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Old 03-05-2018, 07:09 AM   #14
95 S_Trucker
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Re: Lets talk Catalytic Converter positions

I couldn't find anything on my walker catalog, which tells me that walker isnt making the parts to keep a factory exhaust on these 92-95 K200 Suburbans with the 7.4

I did look up this picture on my 92 light truck service manual. This was in the suburban section. 8600 GVW with the 7.4. It clearly shows the converter behind the muffler.

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Old 03-05-2018, 08:03 AM   #15
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Re: Lets talk Catalytic Converter positions

Maybe this will help. I scanned this pic out of my '89 Chev truck shop manual. Maybe this cat is some type of "afterburner".
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Old 03-05-2018, 09:21 AM   #16
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Re: Lets talk Catalytic Converter positions

This is from my service manual. ( C2500 5.7 )

I don't know why they needed to jam the converter between the tranny support
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Old 03-05-2018, 09:25 AM   #17
95 S_Trucker
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Re: Lets talk Catalytic Converter positions

You guys are posting exhaust for trucks. The OP has a suburban.
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Old 03-05-2018, 10:32 AM   #18
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Re: Lets talk Catalytic Converter positions

Quote:
Originally Posted by 95 S_Trucker View Post
I couldn't find anything on my walker catalog, which tells me that walker isnt making the parts to keep a factory exhaust on these 92-95 K200 Suburbans with the 7.4

I did look up this picture on my 92 light truck service manual. This was in the suburban section. 8600 GVW with the 7.4. It clearly shows the converter behind the muffler.

Attachment 1759620
Yup, thats the way mine is. But the muffler and cat have been replaced at one time. Have never seen this before. I think I will move it before the muffler. I still cant understand the reasoning behind a 3 yr span of putting it after muffler as I dont see any difference in floor plans, crossmembers, wiring etc.. from other years or from a 7.4 TRUCK.
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Old 03-05-2018, 12:18 PM   #19
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Re: Lets talk Catalytic Converter positions

Quote:
Originally Posted by 95 S_Trucker View Post
You guys are posting exhaust for trucks. The OP has a suburban.
We are very aware of that fact. We're in Kali. That is also a fact. At one time there were 49-state vehicles and there were Calif. only vehicles that were optioned with EGR, AIR, etc. that 49-state vehicles were free of. Maybe that Sub was originally a 49-state vehicle (?).

The big question is why the cat is where it is since the cats normally require heat shielding and heat of 600-800 degrees to work. Even Calif. doesn't require cats on old cars with new engine swaps because the old cars didn't have heat shielding under the pass. area.
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Old 03-05-2018, 03:39 PM   #20
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Re: Lets talk Catalytic Converter positions

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Originally Posted by mountie View Post
This is from my service manual. ( C2500 5.7 )

I don't know why they needed to jam the converter between the tranny support
I had the same problem with my converter laying on the tranny crossmember. I replaced my transmission mount and now I have plenty of clearance.
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Old 03-05-2018, 03:55 PM   #21
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Re: Lets talk Catalytic Converter positions

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I had the same problem with my converter laying on the tranny crossmember. I replaced my transmission mount and now I have plenty of clearance.
What sort of transmission mount - cross member did you get?
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