Goodman GMP075-4 HVAC Shuddering Sound?

Hello all.
This HVAC unit came with our home in Chesapeake, VA. This winter we noticed what sounded like pipes rattling or banging in the walls on the second floor of our 2-floor home. I went into the attic and noticed that the sound was actually coming from within the unit itself - somewhere behind the gas jets. It almost sounds like it is coming from the blower, but I can't tell. The sound starts around 15-30 seconds after the blower starts up. The unit is still working fine, but the sound is terrible, like a "shuddering" or pipes banging. It seems to be getting louder. We are in the process of finding a qualified technician, but thought I'd ask to see if anyone else had this problem or knew what it might be. Any help would be appreciated.
Thank you.
Tony
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This is is Turtle.
Yes I have seen this on the GMP Models of the Goodman twice with the clam shell heat exchanger touching each other inside the burner housing. There is some burner hangers that should stop the burner clam shell tubes from touching each other but some contractor may have removed these hangers which will let the clam shell touch each other only in heating mode. The solution was to pull the heat exchanger and replace it with a free heat exchanger from Goodman but be sure to replace the hanger for the burner clam shell tubes. This problem is only on the GMP series only when made from 1994 to 2000 year models. The two that I had trouble with was the GMP-075-3 and not the GMP-075-4 like yours. Now the two are the same but your's has a 1/2 H.P. Blower motor and my two has a 1/3 H.P. Blower motor on it but the frame and size , and three burner fire chamber would be the same.
Now the noise that it will make is like two empty metal gas cans rattling in the truck of your car. Now in this type problem it will make the noise only in heating mode and if you just run the fan or cooling system it may not make the noise but just about all the time you run the heat it will be noisey.
Now on these models you have a 20 years heat exchanger warrenty on it and should get a new exchanger to replace it with but you will have to pay the labor to replace it.
TURTLE
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You have correctly identified the problem as the blower unit. It has become unbalanced because something has broken or come loose.
wrote:

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Thank you all very much.
Tony

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