Originally Posted by JuicinJake

the difference comes from reduced drivetrain loss... its as simple as that. power holding might be a result of that, but its certainly not the only mechanism for increased power. rotating losses arise from moments of inertia... of which M (mass) and R^2 (radius squared) are the primary factors (along with a shape constant). if everything in the drivetrain weighed nothing, or very infinitesimally small, then there would be no drivetrain loss and a chassis dyno wouldnt read any different than an engine dyno, assuming the same type of dyno and calibration settings and whatnot. since neither situation is possible, the best thing you can do is to reduce it. fwd cars, like the maxima, show greater hp/tq numbers with the same motor/combo than the rwd g35's do. the reason is there is less power lost in the drivetrain. there is less mass tied up in the sum of the rotating parts that ultimately drive the wheels and that is the difference. the engine is making the same power in either case, it just that more of it gets to the ground. if you go put heavy, wide, cast, chrome 20's on your car, you will slow down due to increased rotating mass. if you go put lightweight 15's and race slicks on your car, you will speed up. in a perfect world this would mean a consistent across the board gain, and is best explained like that, but thats not the case in reality, as the loss generated by some rotating components increases with rpm more than others. as i have seen in denchan350gt's dynos with his aluminum shaft, there was a solid 10-20rwhp from 4000-7000 on hill's garage's dyno (i believe dyno dynamics). for reference, this was on a 300rwhp na de combination. i suspect a turbo car would benefit from increased turbo spool times due to the car being more responsive in the lower gears.

Originally Posted by mx592

Astute observation, although the radius of your driveshaft is far far smaller than the radius of your wheels/tires, so a pound saved on the driveshaft has only a tiny effect compared to a pound saved on the wheels/tires.

10-20 whp would really, really surprise me.

Originally Posted by bluedevils95

How about a group buy. I am just waiting on the pricing for the 2nd gen sedan. Got mine measured and they are working it out.

Originally Posted by murderface

First off - Thank you guys for all the research and info in this thread. This is the next step for my G and I am ready to pull the trigger, cash in hand. Long story short carrier bearing is starting to give me some wobble...looks like the rubber is weathered and cracked and i have feel it slowly get worse over time. 2 piece DS assembly has got to go!

So hopefully you guys can help me decide which way to go with my upcoming purchase...

$680.00 - 3.5" Aluminum seems like a decent price and meets same HP rating as CF
$1150.00 - 3.25" Carbon Fiber version seems fair too for the tech lighter/stronger/smaller rotating mass (faster spin up?)

So my questions : What other factors separate the two from a performance stand point? Should i just "Man it up" and go for the CF DL??? It's one awesome piece of hardware but does the material deteriorate over time? Will it start to lose structural integrity with age and weather? My concern being that CF might not last as long as Aluminum but not certain the manufacturing process or level of finish quality. Any insight on this anybody?

Originally Posted by PLENUMCOUPE

Aluminum. Why spend double the money for identical parts made out of different materials. Not understanding the logic here. Ur not in a full blown race car.

Originally Posted by PLENUMCOUPE

Aluminum. Why spend double the money for identical parts made out of different materials. Not understanding the logic here. Ur not in a full blown race car.

Originally Posted by chiapet15

I wanted to play it safe. I don't remember the what the exact critical speed of AL vs CF was for a fixed diameter and length of driveshaft was, but i do remember that the CF shaft's critical speed was at least 3x that of the AL shaft. Also, the coupe driveshaft is pretty long by most standards, which further decreases the critical speed and explains why the stock shaft is a 2pc; Nissan was likely avoiding critical speed issues with having a single, long steel driveshaft. Since I don't know whether there would be vibration issues (even ones that cannot be felt) with having such a long AL driveshaft, I chose to have as much margin as possible. I plan on driving this car for a very long time (until i can afford a new Porsche 911 4S), so I need the drivetrain to last as long as possible and cannot tolerate any vibrations that could shorten service life.

Speaking of safety, if in a serious accident, the CF driveshaft will break up or shatter with much less force than the AL, which reduced the risk of the shaft penetrating the passenger cabin or catapulting the car.

Originally Posted by murderface

From what I was told the "other" company that used to sell Aluminum drive shafts noted that critical speed was at 170. In a few unique cases car owners were tuning their cars to go well above 7500 RPM redline and 170mph and this raised a safety concern. They did not state when they would have a DL option available but noted that they are testing a "beefier" option. (Seriously that's what the dude told me) As far as The Drive Shaft Shop and ACPT i have not seen any notes on critical speed for Aluminum.

Originally Posted by murderface

Thank you! The verdict is in CFDSFTW