aluminum drive shaft - anyone?
 

http://www.axle-exchange.com/inc/sdetail/365

I came across this on my Facebook account
TAX MONEY BACK - SPECIAL] - FREE SHIPPING - $389

DRIVE SHAFT - Aluminum light weight from Axle Exchange

BRZ/FRS Manual: http://www.axle-exchange.com/inc/sdetail/365

BRZ/FRS Automatic: http://www.axle-exchange.com/inc/sdetail/399

Apply code at the checkout: OVR2015 for special discount

Price: $389.75 US (including shipping within USA)

• 3" o.d. Alcoa 6061 aircraft aluminum
• Spicer HD u-joints.
• HD slip yoke and flange all straightened and hi speed balanced.
• These shafts run very true and are rated to 600hp+.
• NEW - Sound deadening insides

Few people have these installed on their cars and are very happy with it. The quality is unrivaled! The acceleration is immediate, the cars feels eager to just jump when push the throttle. The best bang for the buck…like all the other mods wink emoticon.
Subaru BRZ MT
The Axle Exchange in Fairfield NJ is your source for in house driveshaft fabrication, brake parts, clutch kits and flywheels, c-v axles, rack and pinions, pto shafts and more.
axle-exchange.com

I hardly see much talk these days about lightweight driveshafts but I understand they can really shed unsprung weight. Any thoughts on driveshafts all together or this particular product?

I understand the stock shaft is a two piece. Most after market are one piece to save weight. Anyone care to share their experience as to what negative consequences of going from 2 to 1 would have? I mean it must be 2 piece for a reason.

Driveshafts are not unsprung weight...Rotating mass.

Negatives more NVH normally. The two piece won't fold up and jam you in the ass in a severe rear end crash.

jam you in the ass, lol thats funny. Sorry its really early. Then again whats the point in spending this amount of money, is it stronger than the oem one or simply lighter?

I heard a one piece drive shaft causes wear on the transmission of our vehicles and will cause some gasket or something to prematurely fail causing leaks.

Is this true? I can't find the link to who ever posted it, but it was on this forum.

I've been running one for a while from axle exchange. There are some NVH increase at 40mph at light load. It's not pleasant, sounds like a loose heat shield rattling. Other than that, there is a moderate vibration at 95mph which goes away by 100. Haven't gone much past 120 so I don't know beyond that.

Overall, it's a solid mod. I'd do it again in a heartbeat. I have a 10lb flywheel as well. Those two contribute a fair amount of metallic noises but I'm used to them now. The car feels great but its hard to quantify the difference mods like these make. With just about every lightweight drivetrain part the car feels significantly different from a stock car. Most people would be shocked at the initial responsiveness of my car having dumped more than 85lbs of rotating mass.

Lightened drivetrain components do NOT give "biggest bang for the buck" when it comes to increased acceleration/hp-gains per $$.

If you shed 10 lbs from a driveshaft, you will not feel any difference (in car acceleration) compared to removing the same weight from your spare tire.

Not quite right. You will feel a difference when rates of acceleration change(not speed, but rate of change). At steady state acceleration, there is no difference. Reducing drivetrain mass makes the car feel more responsive when you ask for it to accelerate, decelerate and change direction.

Obviously the biggest bang for the buck hp wise is forcing more air and fuel into the engine. These mods are more about feel and immediacy which work well with the character of the car rather than transforming the car.

I have this on my car and IT DOES MAKE A DIFFERENCE. Faster and smoother acceleration off the mark, quick pick up on highway when I want to pass some car! Love it! I would rather spend 400 on a drive shaft with obvious gains than on a gimmicky air intake any day! Yes , the reduction of rotating mass will make a difference. Couple that with light weight pulley and light wheels and you are going to be quick off the mark, I tell you.

This is a great article explaining the science of weight reduction on rotating parts. Part of the reason I decided my upgrade budget would go farther in other places.


http://www.w8ji.com/rotating_mass_acceleration.htm

Yes - Quite right.
Reducing drivetrain mass does NOT Increase hp. It Increases APPARENT hp because when you accelerate the car is lighter.
I still contend that the difference between reducing rotating mass and reducing the same mass anywhere on the car is an imperceptible difference to our "butt dynos".


Then you have a far better "butt dyno" than anyone else.
The article linked above by @Jonsey explains that reducing the weight of a driveshaft from 30 pounds to ZERO POUNDS results in an "apparent hp gain" of 1/4 hp. So even if you could feel a 1 hp difference, you would have had to reduce the weight of your 30 lbs driveshaft to Negative 90 pounds.

Thank you! a voice of reason!

Does reduction in rotating mass help if building a racecar from the ground up - Yes!
Does rotaing mass weight reduction help much as the FIRST things to do to an otherwise stock vehicle - No.
Weight reduction anywhere on the car will help just as much as reducing rotating mass.

A lot of people THINK it helps because it DOES make a difference when just revving the engine out of gear, but that helps close to zero, when you couple that rotating mass back to the road and it NOW has to overcome the VEHICLE MASS.
Accelerating the rotating mass is negligible compared to accelerating the total vehicle mass.
Want proof? Rev the engine with it out of gear then again when it is IN gear - Big difference Huh?

Look at it this way: Can a runner run faster wearing lighter footwear? Yes.
Can a runner run faster by reducing the weight of his socks by 10 grams when his shoes weigh 5 pounds? - No

That's great info for a drag car which only accelerates once in a straight line from a stand still. Whoever wrote the article is not a subject matter expect either. Anyone can google a few calculators and prove facts on a blog, it should not be taken as gospel. He makes no mention of gyroscopic effects or anything other than how rotating mass might theoretically affect a 3000lb drag cars ET.

Actually, the answer to your question is absolutely yes by every scientific measure. The question you are asking is: "Is the result significant?" And dropping 200lbs off this car was easy, that's pretty significant. Dropping 85 pounds of rotating weight was expensive but most of the modifications helped in other ways while also reducing rotating weight (wider wheels, grippier tires, bigger brakes, more robust clutch).

If you really want to go down the rabbit hole for weight loss and gyroscopic forces, precession and other fun physics, look into the world of professional/semi-pro cycling/triathletes. These guys swear by the difference 10 grams can make on a 15 pound bike my friend. The less weight and power you have, the more weight matters. Please see Hellcat vs. Elise.

Try this.

If a cyclist were to do the following two experiments, what would the results be:

Test A - Remove 10 grams from the perimeter of the tire and compare that to removing 10 grams from the seat.

Test B - Remove 10 grams from the wheel HUB and compare that to removing 10 grams from the seat.

What do you think?

The analogy applies this way for our cars:
Remove weight from the perimeter of the flywheel vs same weight removed from the spare tire: Noticeable difference! (removing from flywheel made a significant difference to rotational inertia)

Remove weight from the driveshaft (or the engine pulley) vs same weight removed from the spare tire: NO Noticeable difference!

The problem with the aluminum driveshafts is interference with short shifters. I know it does hit on the TRD quick shift kit, and I have read one or two accounts of issues with the Kartboy shifter.

I had the aluminum driveshaft on my to-do list until this issue arose.