OK, I have a S5 NA Automatic motor, and an S4 TII Trans, I was planning on buying a Racing Beat Aluminum Flywheel. My question is, should I buy a flywheel to fit the S5 motor or to fit the S4 Trans? or does it really make a difference whether I buy an S4 or S5 Aluminum Flywheel? any help will be appreciated.

 

The flywheel has to be the right size for the transmission, and the right imbalance for the rotor weight.

There are three basic different sizes: N/A, Turbo II, and FD. (At least, I'm 90% sure FD has a special flywheel because of the pull clutch) There's two different clutch sizes for N/A but given that all N/A flywheels are for the 225mm clutch, you use that.

Anyway. You need a Turbo II flywheel, because of your transmission. You need a counterweight for a Series 5. So: Series 5 TII flywheel.

However, since the aftermarket flywheels bolt to an automatic's counterweight, just tell them it's for a Turbo II and you already have the correct counterweight. Done.