Norcal - I just had 3.73 put in mine last week and the guy that put them in for me said that they are worn if they have sharp edges along the larger end of the pinon. I don't know if this is correct but when you set the old and the new side by side the new has a blunt flat edge along the top of the gear...
As for the 3.73 I highly rec. picking a set up. This is like driving a different car.
I hope that helps or with asking the ? will get the correct answer......Good Luck
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