And some of us just don't have junkyards nearby with 40+ year old cars in them...

The sad thing is that you really can't make an honest opinion without replacing a good stock one with the aluminum or carbon fiber one... All you can say is yup, now it works.

Lowering the rotating inertia weightl allow u to put a little more power to the wheels. So my slip yoke on my sdriveshaft is bad. Instead of getting a used part. Id rrather go with an upgrade. My car is far from stock at this point.

Lowering rotational inertia does not put any more power to the wheels.

Lowering the rotating inertia weightl...

Actually, I think it will allow you to send more shock load to the differential. Less mass to damp engine engagement through the clutch. Probably won't matter unless you're drag-racing, although I could see a higher modulus material transmitting higher frequency noise. Might be noisier, but I haven't seen any accounts. I have read stories about the aluminum shafts not liking harsh treatment through the clutch. Apparently the u-joint yokes can get damaged.

You can buy a slip yoke and have a new steel shaft made for ~$250 bucks easy I would guess. I have found a local guy, up the Gorge (Portland talk...) who would shorten one for $90, which turned out to be essentially building it over again after cutting it. A good shop could probably source the yoke too. Just take your old one in and say "make me a copy of this, please". You might be spending more money than necessary for a relatively simple part.

Iv'e done an aluminum driveshaft before (not on a Z) and it did make a noticable difference in performance. The throttle response felt quite a bit better and overall the car just felt lighter due to the quicker acceleration, especially in the corners. It's nothing like a light weight flywheel but worth doing if you have already done most of the major mods.

Lowering rotational inertia does not put any more power to the wheels.

Really? So the power used to accelerate the driveshaft is not decreased by lowering the rotational inertia and therefore more of the engine's power is not available to accelerate everything else?

At steady state you are correct though.

Really? So the power used to accelerate the driveshaft is not decreased by lowering the rotational inertia and therefore more of the engine's power is not available to accelerate everything else?

At steady state you are correct though.

Leon is correct. There is no more power. There is just an increase, however large or small in efficiency. Somewhere, there is probably a trade though. Maybe they only have a service life of 5 years, there is always a trade off.

Leon is correct. There is no more power. There is just an increase, however large or small in efficiency. Somewhere, there is probably a trade though. Maybe they only have a service life of 5 years, there is always a trade off.

"Lowering the rotating inertia weightl allow u to put a little more power to the wheels."

Note the part about more power to the wheels. Less of the unchanged amount of power available from the engine is used to rotationally accelerate the lighter driveshaft leaving more available to be used at the wheels. No more total power. More available at the wheels during acceleration only. Just like reducing friction in a transmission doesn't give the engine more power but just leaves more available to do useful work.

Steve

"Lowering the rotating inertia weightl allow u to put a little more power to the wheels."

Note the part about more power to the wheels. Less of the unchanged amount of power available from the engine is used to rotationally accelerate the lighter driveshaft leaving more available to be used at the wheels. No more total power. More available at the wheels during acceleration only. Just like reducing friction in a transmission doesn't give the engine more power but just leaves more available to do useful work.

Steve

Ok, Leon is still right, there is no more power being made, and you have restated what I said which is that "there is just an increase, however large or small in efficiency." You're correct. You'll probably want the last word but I agree, there is an increase in efficiency under acceleration. 8)

Lowering rotational inertia does not put any more power to the wheels.

Really? So the power used to accelerate the driveshaft is not decreased by lowering the rotational inertia and therefore more of the engine's power is not available to accelerate everything else?

At steady state you are correct though.

Ok, Leon is still right, there is no more power being made, and you have restated what I said which is that "there is just an increase, however large or small in efficiency." You're correct. You'll probably want the last word but I agree, there is an increase in efficiency under acceleration. 8)

Obviously Leon did not say "there is no more power being made" so I'm not sure how he can be "right" about something he didn't say. Maybe you didn't read what either Leon or I wrote.

Your statement about efficiency is just another way of restating my original rhetorical question to Leon.

So what exactly have you added to this?

Steve

And there you have it, 'the last word.'

And there you have it, 'the last word.'

That's ironic. The guy who said I wanted the last word not being able to resist commenting one more time. This post gives you the opportunity to actually let me have the last word. If you think you can.

Steve