[Xinshadow]

Originally Posted by Caspeed

The ony time a lighter driveshaft will have any effect on shifting is if your car has a driveshaft between the clutch and the tranny. Think Porsche 928.

Double clutching matches the speed of the input shaft with the next gear on the output shaft, which is turning at diff speed. That is all.

Reducing rotational mass is generally a good thing. But remember that it's effect is determined by it's moment of inertia. The further from the center of rotation the greater the effect. 5Lbs from a wheel/tire assembly will be greater in it's effect (not even counting unsprung weight) than 5Lbs on a driveshaft.

That makes sense, its probably a placebo effect from lighter overall weight then. I have a buddy who has a brz he insists on maintaining as stock, so once a year I'll drive his car against mine to see how I'm coming along performance wise. My car is definitely easier to heel-toe, which I attributed to the driveshaft but given this info its more likely that this is just a side effect of the cumulative change in powerband and lower weight on my car due to all my mods as a package.

That said, if you're trying to strip weight off the car, I see no season why you wouldn't jump on this for less than $400. It would be silly to do a lightweight flywheel, upgraded clutch, and not do the driveshaft since you're down there anyway.