Spring noise when closing window

A quick learner from San Francisco says:
I ordered a few S351 27" Sash balances. I have installed them and the weight seems right. When closing the balance the springs make a loud twang noise.
Youtube video http://youtu.be/dq68VzpiqpY

Strictly I think I should have ordered the S390, but I don't think that this is the issue as there is a very small difference between the two. A picture of the old Caldwell sash balance is attached.

Before I order some more sash balances can you suggest why this could be the case.
User submitted photos of a window balance.
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Paul from SWISCO responded:
Sorry to hear you're having trouble. Looking at your order, you ordered two different weights. Which one is giving you the issue? It also appears that you ordered S351-28 balances, not S351-27. Can you confirm what you have?
A quick learner from San frnacisco says:
I installed S351-28 option 2760. So you are right they are 28" and match the length of the metal for the balances being replaced.

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Paul from SWISCO responded:
Thanks! I checked our inventory for the the S351-28 2760 balances and the spring movement is quiet on every part I checked. We also use a recessed chord hook on the balance so that the knot doesn't rub on the track. I'm at a loss for why it's making noise.

Does the window track have any dents or cuts? Is it hard to lower the sash because the spring strength (2760) is too strong? Keep in mind that a stamp option of 2760 can carry a window sash weight of 30 through 33 pounds. Finally, is there too much play with the sash (side to side, specifically) when operating? These are questions from the balance manufacturer. Please let me know and we can work from there!
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