Lets talk Catalytic Converter positions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

manimal · 03-03-2018, 10:56 AM

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?
Thanks

b454rat · 03-03-2018, 10:58 AM

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.

manimal · 03-03-2018, 11:19 AM

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.

Tom · 03-03-2018, 02:08 PM

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.

95 S_Trucker · 03-03-2018, 04:42 PM

Every 92-95 3/4 ton suburban that I have worked on had the cat at the rear behind the muffler.

manimal · 03-03-2018, 05:14 PM

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.

**Mr_Rich** · 03-03-2018, 05:41 PM

Quote:

Originally Posted by 95 S_Trucker

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.

95 S_Trucker · 03-03-2018, 06:11 PM

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.

**1968k20** · 03-03-2018, 09:31 PM

My '89 K3500 Single cab/single rear wheels has the cat behind the exhaust near rear axle

b454rat · 03-04-2018, 08:33 AM

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.....

mountie · 03-04-2018, 08:09 PM

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)

arrg · 03-04-2018, 11:34 PM

Couldn't find the Suburban, but the 3500 checks out. Converter behind the muffler.

manimal · 03-04-2018, 11:50 PM

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?

95 S_Trucker · 03-05-2018, 07:09 AM

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.

Name: exh.jpg
Views: 1258
Size: 59.7 KB

**Mr_Rich** · 03-05-2018, 08:03 AM

Maybe this will help. I scanned this pic out of my '89 Chev truck shop manual. Maybe this cat is some type of "afterburner".

mountie · 03-05-2018, 09:21 AM

This is from my service manual. ( C2500 5.7 )

I don't know why they needed to jam the converter between the tranny support

95 S_Trucker · 03-05-2018, 09:25 AM

You guys are posting exhaust for trucks. The OP has a suburban.

manimal · 03-05-2018, 10:32 AM

Quote:

Originally Posted by 95 S_Trucker

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.

**Mr_Rich** · 03-05-2018, 12:18 PM

Quote:

Originally Posted by 95 S_Trucker

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.

arrg · 03-05-2018, 03:39 PM

Quote:

Originally Posted by mountie

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.

mountie · 03-05-2018, 03:55 PM

Quote:

Originally Posted by arrg

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?

03-03-2018, 10:56 AM	#1
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	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? Thanks __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

03-03-2018, 10:58 AM	#2
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	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. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

03-03-2018, 11:19 AM	#3
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	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. __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

03-03-2018, 02:08 PM	#4
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,689	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. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

03-03-2018, 04:42 PM	#5
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,178	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.

03-03-2018, 05:14 PM	#6
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	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. __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

03-03-2018, 06:11 PM	#8
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,178	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. Last edited by 95 S_Trucker; 03-03-2018 at 06:17 PM.

03-03-2018, 09:31 PM	#9
1968k20 Senior Member Join Date: Dec 2009 Location: Chester,California Posts: 5,618	Re: Lets talk Catalytic Converter positions My '89 K3500 Single cab/single rear wheels has the cat behind the exhaust near rear axle __________________ 1977 Chevrolet K10 SWB Project 350/4spd/np205 1977 Chevrolet K20 LWB 350/350/203 1991 4Runner 22RE 5 SPD Yanmar Tractor 3 Cyl Diesel

03-04-2018, 08:33 AM	#10
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	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..... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

03-04-2018, 08:09 PM	#11
mountie Registered User Join Date: Jun 2011 Location: Bradenton, Fla. Posts: 1,100	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) __________________ '70 GTO Midnight Blue '88 GMC Sierra SLE 392,000 miles-(2018) sold to Classic car shop in Germany. '93 Cadillac STS Black '93 Mercedes SL 500 Teal '86 Yamaha FZ750 - 15,000 RPM '86 Yamaha FJ1200 - Criminally Fast 2016 Ferrari 488 GTB, I drive it - don't own it. '05 GMC Yukon XL , SLT 4wd ( just purchased 2018)

03-04-2018, 11:34 PM	#12
arrg Registered User Join Date: Feb 2016 Location: Omaha, NE Posts: 38	Re: Lets talk Catalytic Converter positions Couldn't find the Suburban, but the 3500 checks out. Converter behind the muffler. Attached Images __________________ 1988 Chevrolet C1500 RCSB

03-04-2018, 11:50 PM	#13
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	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? __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

03-05-2018, 07:09 AM	#14
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,178	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.

03-05-2018, 08:03 AM	#15
Mr_Rich Registered User Join Date: May 2006 Location: Santa Maria, Calif. Posts: 781	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". Attached Images __________________ 1989 K1500 Chev. EC Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit. 2009 Hummer H3T 3.7L 5M (sold) 1997 K2500 Chev. EC 7.4L/ 4L80E 2018 Dodge Ram 2500 HD R/C

03-05-2018, 09:21 AM	#16
mountie Registered User Join Date: Jun 2011 Location: Bradenton, Fla. Posts: 1,100	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 Attached Images __________________ '70 GTO Midnight Blue '88 GMC Sierra SLE 392,000 miles-(2018) sold to Classic car shop in Germany. '93 Cadillac STS Black '93 Mercedes SL 500 Teal '86 Yamaha FZ750 - 15,000 RPM '86 Yamaha FJ1200 - Criminally Fast 2016 Ferrari 488 GTB, I drive it - don't own it. '05 GMC Yukon XL , SLT 4wd ( just purchased 2018)



Register or Log In To remove these advertisements.

03-05-2018, 09:25 AM	#17
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,178	Re: Lets talk Catalytic Converter positions You guys are posting exhaust for trucks. The OP has a suburban.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Register or Log In To remove these advertisements.