cam/rear end ratio question

[dagamore]

I am thinking about putting a different cam in to my 09 g6, and was wondering why some of the cams state that you need a higher rear end on the car. Why would i need to go from my 3.55 to a say 3.73 or better?

 

[TonyN]

Generally cams move the power band and peak HP to higher RPM's. Sometimes you can even lose low end power depending on the type of cams. Gears get you to your power band faster making up for the changes. Manufacturers recommend gears to take full advantage of the there product. It is highly suggested that you take there advice.