I have an 07 Duramax while my brother has an 05, both of which have blown speakers in the doors. I was lookin for some advice on where to replace and/or how to fix the problem. Sounds like crackle or a pop whenever it its turned louder and whenever the bass would hit. Any advice would be great...

sounds like a ground not making the connections.....i have an o3 and it isnt that difficult to get the receiver out......dunno about yours tho..

you also would be better off replacing the stock POS's with ANYTHING aftermarket.... the speakers should be 6 3/4....a 6.5 should work too...makes a big difference for like 20-30 bucks a pair

deffinetly go with some aftermarket ones if there blown! alot of good ones are out there diamond audio,jl audio,pioneer,boston acustic etc... go on ebay and you can get some good deals on component sets

What size speaker are in the front and rear (extended cab)?

You've definitely got bad speakers. Happened on a couple here. As mine are fleet vehicles with Am/Fm onlys, I replaced with stock. IIRC, around $30. You'll probably want to upgrade, and the OEM one clips in, so you'll probably have to drill holes. I'd use the CRUTCHFIELD website to see what fits. I buy there because they take all the install "thinking" out of the equation, and have very good customer service. At minimum, you can see what fits.

I've never had "snap, crackle, or pop" from the factory radio failing, only from blown GM speakers.

The door speakers blow,in my opinion ,because the door dinger goes through them.Replace with aftermarkets and replace radio with aftermarket and they will last longer.Front doors are 6 3/4 or sometimes called oversize 6.5. Rears are 4x6.

Thanks a lot...I'll look into all of the above