Alright my impala has a terrible rattle that sounds like its coming from right under the drivers seat but only happens when it is first started and then quiets down... Anybody know what this could be... And what are some exhaust mods you have done, something that sounds good but not too loud on the highway

i got it too. took the dealer. they couldn't find anything.

Mine does it also, on start up and shut down.
Have not taken it into the dealer yet.
If they find a solution I will post it here.

Jim

Welcome!

I took it to a dealership... Said they heard it and don't know what it is... Took it to a muffler shop, said he didn't hear it, that that's just the way they are supposed to sound.... I personally think that it is the cat, as it warms up, it quits rattling

Check the catalytic converter heat shield. It may be loose. I have an '09 LTZ and never had any exhaust rattle.

sound like a light sabor from starwars? Mine did that for about 10,000 miles then just quit. It would do it real bad on first start in the morning after it set all night.. usualy lasted abour 30-45 seconds. Then in real cold weather ( under 30* ) it would do it at red lights ever now and then.

My exhaust also smoked for ever, like steam when its cold... it still does that no matter what the temp is, also i always have small puddles of water under them its done that from day one.

FYI, I have a 2013 Impala LTZ. Does the same thing. ONLY when started up when the engine is cold, lasts for all of 4 seconds, then you never hear it again. Also, it doesn't make the sound when you drive either. It's only when started up.

Very strange...

my 2013 LT does it too! I've thought about replacing the exhaust.. or detach the exhaust at the manifolds and see if its still there. somewhat glad to hear that it wasnt just mine.. thought it was a sign of things to come.

FYI: There is a TSB on this issue and GM is well aware of it. I was advised it is the double wall of the y-pipe and there is no fix. They "can" replace the y-pipe, but new y-pipe has same design with potential for same issue. Goes away relatively quickly once car is started and moved a little, but I agree, annoying just the same.

My '14 LTZ Limited has done it since I bought with 8900 miles on it, but have decided to just deal with it if GM doesn't have a good fix or better y-pipe solution...

Actually, not sure if it is considered a "TSB" or something else, but here is the wording I got from the Service Manager at local dealership, finally:

2014 Chevrolet Impala Limited (VIN W) [2G1WC5E30E1101187] | Impala Limited Service Manual 7132776 | Document ID: 3671083
#PI1138: Rattle/Noise from Front or Rear of Vehicle on Cold Start Up - (Dec 20, 2013)
Subject:
Rattle/Noise from Front or Rear of Vehicle on Cold Start Up

Models:
2012-2013 Chevrolet Impala
2014 Chevrolet Impala Limited

Condition/Concern
Some customers may comment on a brief rattle or noise heard from the front or the rear of the vehicle on a cold start up.

This may be caused by the “Y” pipe inner and outer components expanding at different rates resulting in the rattle/noise.

Recommendation/Instructions
This is a normal characteristic of the vehicle’s exhaust system and no repair(s) should be attempted for this concern.

Customer Information
Please communicate to the customer this condition is a normal operating characteristic of their vehicle. It will not impact the designed performance or reliability of the vehicle. Please share this information with the customer, including a copy of this message.

For further information, please contact GM Technical Assistance Center (TAC) for assistance.

Eric, thanks so, so much for this. I guess this is what we've all wanted to hear from GM, at least that they acknowledge this is an issue in the form of a TSB, document, or something.

That's why I put a Magnaflow catback on lol. When I took my OEM exhaust off you could see it was double walled in some places not in others. I also like that the Magnaflow has a even Y pipe instead of the offset of the factory exhaust.

I didn't know Magnaflow made a pre-cat Y-Pipe? The rattle that most hear and is covered in the GM document, is the Y-Pipe that goes from the exhaust manifolds to the cat. I thought Magnaflow only offered a cat-back exhaust option...

What is the purpose of a "double walled" exhaust pipe in the first place? Just added strength or something?

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This is exactly what i needed to read!, Thanks! Now time to stop worrying about mechanical issues and order that CAi. The wife and I just bought a 2013 Impala LTZ Black 4 days ago, and I noticed this sound, So glad to know I didn't get ripped off LOL.