Stock Exaust Stainless or Aluminized?

Shemmy · August 19, 2003

I had an exaust shop tell me that my stock exaust system is aluminized steel and not stainless. I thought it was stainless. So what is it?

Rammer · August 19, 2003

It's stainless, not sure what grade though.

simple · August 19, 2003

I would think that it's stainless. Call the dealer and see what they say.

Shemmy · August 19, 2003

Man, this guy at the shop I went to is really ticking me off. First he told me that my exaust system is aluminized and then he tells me that the 70 series flowmaster muffler is crap and will drone at crusing RPMs. Are there any problems with welding in an aluminized muffler to a stainless exaust system?

Taki · August 19, 2003

Im pretty sure that Flowmaster makes stainless steel mufflers now....at least their website says they make them...

BDBWTE · August 19, 2003

I had an exaust shop tell me that my stock exaust system is aluminized steel and not stainless. I thought it was stainless. So what is it?

It's stainless.

Shaners · August 20, 2003

GM uses a low grade stainless on their exhaust systems. They will show some discoloration and maybe some light rust, but they will last a long time...

Victory Red · August 20, 2003

Are there any problems with welding in an aluminized muffler to a stainless exaust system?

Yes there are. First you have disimilar metals there. Can you say corossion? And secondly, I'm not 100% sure, but I don't think you can weld aluminum & stainless steel together.

You probably have the stainless system. If it has ANY rust spots on it, it's stainless. Aluminum will not rust, it corrodes (white colored oxidation). It's very easy to tell them apart.

bigtruck21 · August 21, 2003

aluminized steel not aluminum. I'm pretty sure aluminized steel and stainless steel will weld together. But if you have a stainless system like mine, why put on a muffler that will need to be replaced sooner?

Shemmy · August 21, 2003

I decided on a stainless magnaflow. I will cost less that an aluminized flowmaster and it will have a more mellow tone.

Highbeam · August 21, 2003

I have aluminized pipes welded onto the stock stainless piping. No problem, no rust, holds up real well. Done with a mig welder.

Then at the end I have stainless tips welded on to the aluminized pipe and there is more corrosion here. Hasn't rusted through in the last couple years though.

The welder punches through the aluminum coating and welds the iron in the center of the aluminized pipe to the iron in the stainless pipe with a steel bead. Stainless steel isn't that much different than regular steel.

bigtruck21 · August 25, 2003

I decided on a stainless magnaflow. I will cost less that an aluminized flowmaster and it will have a more mellow tone.

let us know when you get it and how you like it for sound/performance.

Shemmy · August 26, 2003

I got my magnaflow muffler welded into the stock system this afternoon. I haven't had a chance to take it on the highway yet to see if it will drone, but I highly doubt that it will. Inside the cab it sounds deep and mellow and at idle it is barely audible. I'll have someone do a drive by for me so I can hear what is sounds like outside. So far I am very pleased. I wanted something a little louder than stock and that is what I got. I didn't notice any major changes in performance. The truck does seem to idle extremely smooth now. I actually thought that it stalled at one point. Hopefully the MPGs will increase which is the main reason for doing this (or so I told my wife).

The part number for this muffler is 14589. This is the 5 X 11 X 22 oval stainless magnaflow. The outlets are 3" and it is in the center/offset configuration. I can see where this might not be loud enough for some people.

bigtruck21 · August 27, 2003

sounds good...keep us posted on the mileage if you can keep your foot out of it

nateh · August 31, 2003

The system is 409 stainless steel. 409 develops surface rust quickly, but doesn't corrode further for a long time. Some systems have an aluminized coating on the stainless, which inhibits the surface rust formation. GM made the transition to full stainless years ago.

Flowmaster makes a few stainless systems, but a lot of their stuff is still aluminized or regular mild steel. Incidentally, the company that makes the OEM exhaust and Flowmaster are both subsidiaries of the same parent company.

You can indeed weld mild steel to stainless. If you use the wrong weld wire, you can have some problems with a corrosion at the weld in the long term. Most of us will not notice the corrosion in the time frame the exhaust is on our vehicles. As a rule of thumb, you use weld wire made from the same grade as the highest in the combination. For welding 409 to cold-rolled steel, you would use a 409 based weld wire.