Best exhaust system, muffler resonator tailpipe

Camdo

Well-Known Member
2005 GMC Envoy SLT, 4.2 L inline 6 cylinder engine.
After 3 years of service, my Walker stainless steel muffler and rear muffler / resonator has failed. The failure is a rotted pipe between the muffler and resonator. The pipe is an integral part of the resonator. Even though the resonator is made of stainless steel, the pipe is just steel. I knew this when I purchased it but thought Walker knows what it is doing and has figured out that steel pipe will last as long as the ss mufflers. That was definitely a wrong assumption. Both the muffler and resonator look okay on the outside.

I want to replace the exhaust system with something that will last, and looking for suggestions as to the best manufacture for longevity. Please state how long your system has lasted.

I am considering UPSW Auto Parts stainless steel system, but details are lacking. Does anyone have experience with this product? https://www.upsw.com/stainless-steel-exhaust/gmc/envoy/?year=2005&trim=SLT Sport Utility 4-Door&en=4.2L 256Cu. In. l6 GAS DOHC Naturally Aspirated
 

Mooseman

Moderator
No experience however, looking at the muffler, it seems to be necked down going into it so there may be some increased back pressure and reduced flow. The OEM was 2.75", however some aftermarket systems are 2.5" or 3" with a necked down muffler, like in the Walker.

You could contact them and ask what pipe size they use on this system and if it is really necked down inside (it could be double walled). They seem to be performance oriented, boasting they use mandrel bent pipes. The price is very reasonable. A similar JBA system is more than double the price.
 

Chickenhawk

Well-Known Member
Northeastern Exhaust is made in China. Based on reviews, it seems to be good stainless steel (non-magnetic; unlike the Walker SS) but hangers and gaskets seem to be cobbled on without exact placements, so there may be installation problems. If it was me, I would certainly give it a try. Let us know. I don't think anyone in here has found a really good, high quality, true stainless system that does not restrict flow.
 

Mooseman

Moderator
I don't think anyone in here has found a really good, high quality, true stainless system that does not restrict flow.
The JBA system is a 3" high flow non-restricted system but double the price. Loud muffler too. It doesn't keep the polished look at all with surface corrosion. I still have the one I had on the '02 but has been stored outside. If I do reuse it, I'll be looking for a better muffler other than performance ones. Tried the JBA, Magnaflow and Dynomax and all sounded like ricers. The Dynomax has an internal flap that's supposed to reduce drone while cruising but the internal spring failed.



 

littleblazer

Gold Supporter
I used the walker on the envoy. I noticed no difference between it and stock before the stock one blew out. I think mpg went up a tad honestly.

As long as you aren't spinning the thing to redline, the neck down to 2.5 is fine. Its far enough back in the exhaust stream anyway. The walker still isn't as quiet as oem either. I'd imagine the louvered interior is more open than stock so it kind of equals out.
 
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Camdo

Well-Known Member
I wanted a stainless steel exhaust system for a reasonable price for it to last the lifetime of my vehicle. Here is a comparison chart of exhaust materials from Summit Racing website https://help.summitracing.com/app/answers/detail/a_id/4773/related/1
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My experience with the Walker aluminized steel connector pipe in Boston MA was 3 years which is the bottom of the range expressed in the chart. Best longevity is 304 stainless steel (which is non-magnetic) but I could not find a manufacturer that made a quiet OEM style replacement exhaust system for the Envoy 4.2L. The ones I saw were performance orientated and pricey. Next in the chart is 409 stainless steel (which is magnetic) with an expected life of 8 years. That looked good to me with much better lifetime than aluminized steel.

I could find only one manufacturer, Northeastern Exhaust, that made a stainless steel quiet / family / no growl type exhaust system. I wanted a clear unambiguous statement of what the connector pipe is made of. I did not want a repeat of Walker’s deceptive description of a stainless steel system where the connector pipe is actually made of aluminized steel. Distributor UPSW.com (mentioned in post #1 of this thread) did not respond to my inquiry.

The only seller I could find that clearly stated their product was an all 409 stainless steel system was Time Auto Parts on ebay. http://rover.ebay.com/rover/1/711-53200-19255-0/1?icep_ff3=2&toolid=10001&campid=5338077216&icep_item=282742894871
I sent them a private message for confirmation (shown below).
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Here is a picture of the exhaust system. It came nicely packaged in a box and arrived undamaged. I got it fast on the 2nd day after ordering on ebay.
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All the pieces, except the pipe clamps, were marked stainless steel. Of particular interest was the connector pipe also marked stainless steel. I wish there was a simple definitive test for 409 stainless steel. It contains a lot of iron and is magnetic. It is called stainless steel because it contains 11% chromium and so, will resist rust better than plain steel or aluminized steel. My method for confirming if the parts were if fact made of 409 stainless steel was visual. On the connector pipe, I could see a glistening, where the tubing is clamped to form the bends, as if diamond dust was on the metal. I believe this is chromium sparkling, and so conclude to my satisfaction that it is indeed 409 stainless steel. On the muffler and resonator, I could see the tell tale soft dull sheen that only stainless steel sheet metal makes. I was satisfied everything, except the 2 pipe clamps, were made of 409 stainless steel. Also take note that the bends in the connector pipe are smooth inside mandrel bends compared to the Walker wrinkle bends.
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Here are the part numbers:
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The pipe outside diameters are as follows:
Catalytic flange pipe 2.855
Muffler entry 2.420
Muffler exit 2.625 .057 wall
Connecter pipe 2.495 .056 wall
Resonator entry 2.475 .056 wall
Resonator exit 2.530
Tailpipe 2.710

There is a neck down at the muffler entrance. The dimensions are no different than the old Walker system including the neck down.
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I got an exhaust pipe tool set loaner from Advance Auto Parts. Thank you Advance Auto Parts. The Powerbuilt Kit 42 4pc. Exhaust Pipe Tool Set. A very nice high quality tool kit. I was tempted to buy it.
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I tested the pipe fit and used the large expansion tool to get it to slip in. Better to do this on the shop floor rather than under the vehicle. I also marked the pipe full insertion length with a sharpie pen. It is always a wonder if you have fully inserted the pipe before clamping tight.

I jacked the vehicle on the passenger side and set the jack stands.

Removed the rear tire

Removed the frame cross bar that runs under the muffler.

I used the Powerbuilt cutter to sever the pipe near the muffler outlet. I was surprised how easy it was to cut.

Removed the two nuts from the muffler flange and tilted the muffler while wriggling the mounting bar from the rubber hanger. Came off without a problem.

Wriggled the connector pipe from the rubber hanger in similar fashion.

The resonator had fallen off all on its own from a rotten connector pipe.

Here is the old Walker Quietflow stainless steel exhaust system, 3 years in service in Boston MA. Note the connector pipe is aluminized steel and not stainless steel as name might imply. The muffler is pitted but solid, and the resonator is in excellent condition. I assume Walker used 409 ss to make the muffler and resonator.
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Continued in next post
 
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Camdo

Well-Known Member
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Installation of the new Northeastern Exhaust system was straightforward. I was concerned about the three piece assembly being difficult to align, but that was not the case at all. In fact it was easier than the one piece resonator connector pipe configuration of other manufacturers. The trick is that the hanger rod where it sits on the rubber mount is parallel to the bottom of the vehicle (level). The system installed perfectly into the vehicle without any problems.
  • Clean the catalytic flange matting lips with a power brush.
  • Install the muffler but leave the bolts loose and slack. Use muffler sealant on the flange lips. Use dish soap on the hanger rod to ease installation thru the rubber hanger. Slip the hanger rod thru the rubber hanger and then fit the flanges. Leave space at the flanges do not squeeze out the sealant yet. Block the rear of the muffler for support.
  • Install the connector pipe. There is no trouble fitting it up and around the rear axle. An advantage of the 3 piece design. Use dish soap on the hanger rod. Install the hanger rod into the rubber hanger and then slip the end into the muffler. Twist the connector so the hanger rod is level to the bottom of the vehicle. This is perfect alignment. Do not tighten pipe clamp yet.
  • Install resonator. Use dish soap on the hanger rod. Install the hanger rod thru the rubber hanger and them slip the end into the connector pipe. Check clearance between vehicle frame and top of resonator (.50 inch minimum) and twist for proper visual orientation of tailpipe looking at vehicle rear end. There is a generous slip fit to make adjustments. Hanger rod should be level with bottom of vehicle.
  • Tighten muffler flange 33 ft-lb. Tighten muffler pipe clamp 33 ft-lb. Check resonator alignment. Tighten resonator pipe clamp over slotted portion of pipe end 33 ft-lb.
  • Install the vehicle frame cross bar that runs under the muffler 37 ft-lbs.
  • Install rear tire 100 ft-lbs.

I am pleased with the performance of the exhaust system. It is a quiet system comparable to the Walker Quiet Flow, and GMC OEM system, suitable for a family. There is no growl.
Job cost and time:
Exhaust system…$211.38
Loaner tool……………….. 0 Thank you Advance Auto Parts.
Muffler seal…………….… 0 Left over from 3 year ago when I installed the Walker system.
Total cost……….…..211.38

Installation time 5 hours includes making space in my garage and putting everything back at end of job, taking pictures and making notes.

Time will tell how long this Northeastern Exhaust 409 stainless steel exhaust system will last. I know a Walker system will last 3 years so anything longer is going to be a plus. At the time of this writing I would have paid $260 for a Walker system. So for less money I got an “all” 409 stainless steel system of comparable performance.
 

Wooluf1952

Well-Known Member
One thing I've noticed with 409 SS: While a magnet will stick to it , it is much easier to pull the magnet off of 409 SS than it is to pull that same magnet off of plain or aluminized steel. :twocents:
 

Mooseman

Moderator
Nice find and a very good price for a complete SS system. Too bad it comes with the trash can resonator but you were looking for quiet so this works for you.
 

gmcman

Well-Known Member
@Camdo Can you take a pic of the inside of the muffler inlet? Curious to the diameter.

@littleblazer I had the Quiet Flow on mine and was necked down considerably. Walker offers a different system, not sure of the name, but I don't believe that one was necked down much, if at all.

I lost a couple MPG's right off the bat, and this could be the fact my 60 MPH cruise is 2000 RPM with my 4:10. Either way, it felt peppy off idle but deteriorated after that.

Nice to see a full SS system, curious to the results. Thanks for the pics. :thumbsup:
 
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Camdo

Well-Known Member
@Camdo Can you take a pic of the inside of the muffler inlet? Curious to the diameter.
Unfortunately I did not take a "down the tube" picture of the muffler inlet, but I did measure the pipe outside diameters and have a good idea what the wall thickness is, having measured the pipes in other areas.

The large diameter leader pipe attached to the flange is 2.855 OD with a wall thickness of .056 so that would be 2.743 ID.

The leader tube necks down to a short muffler inlet tube which measures 2.420 OD with .056 wall so that makes it 2.308 inside diameter.

So from a gas flow perspective the flow starts with diameter 2.743 and necks down to 2.308 inches as it enters the muffler.

My recollection was that the neck down was as it appears on the outside view. That is there is no double wall.

The muffler appeared identical to the old Walker Quiet Flow.
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gmcman

Well-Known Member
Yeah, looks the same.

This is the quiet flow muffler inlet and outlet. Looks good on the outside until you get to the guts of the chamber.

Inlet:
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Outlet:


Screenshot_20200701-161307_Chrome.jpg

Sidenote, the Walker system people did like was the FX. Found that in an old post.
 
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Camdo

Well-Known Member
Yeah, looks the same.

This is the quiet flow muffler inlet and outlet. Looks good on the outside until you get to the guts of the chamber.

Sidenote, the Walker system people did like was the FX. Found that in an old post.
I believe the FX was steel and not stainless steel.

The Walker outlet picture looks like substantial restriction, or is that an optical illusion looking down the full length of the tube?
 

littleblazer

Gold Supporter
@Camdo Can you take a pic of the inside of the muffler inlet? Curious to the diameter.

@littleblazer I had the Quiet Flow on mine and was necked down considerably. Walker offers a different system, not sure of the name, but I don't believe that one was necked down much, if at all.

I lost a couple MPG's right off the bat, and this could be the fact my 60 MPH cruise is 2000 RPM with my 4:10. Either way, it felt peppy off idle but deteriorated after that.

Nice to see a full SS system, curious to the results. Thanks for the pics. :thumbsup:
Yea, the one I used I do not recall looking that bad inside... that photo you showed is pretty bad. :dunce:
 

gmcman

Well-Known Member
The Walker outlet picture looks like substantial restriction, or is that an optical illusion looking down the full length of the tube?
Not an illusion, I can see how the ID could appear that way. Don't remember what I used, but I lowered something inside to gauge and was just under 2" IIRC.
 

MRRSM

Lifetime VIP Supporter
In this supporting Video, the VOP (Video Original Poster) echoes the R&R of this repair...and answers the Question:

"Can My Car (SUV) Catch On Fire from an Old Exhaust System?"

There are some interesting views on the use of 110 AC Powered Milwaukee Sawzall to expedite removing the Old, Rotted CAT-Back Exhaust System. Note the Heat Damage to the Under-Body Muffler Assembly Heat Shield:

 
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