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iTrader: (17)

Here is a hypothetical thought for you guys on the Steel vs. Aluminum deal.

Everyone knows that flywheels all have different weights right? Some are super light some are super heavy. Why? Well frankly it all depends on your kind of racing. Some folks say that a heavy flywheel will give you more momentum during a 1/4 mile race rather than a 1/8th.

Perhaps we could use this same concept for the D/S's. More weight = more momentum during a pass.

As you are racing, and while you shift (hypothetically) in that split moment you let off the gas, you lose a little momentum of that light shaft that would help keep the wheels turning and give it less friction or force holding it back.

As for the Steel shaft would be heavy and for that split second, the mere weight would keep the wheels turning perhaps faster as the momentum would be greater than the aluminum counterpart.

This is all just a hypothesis. But think about it, it would explain why aluminum has no beter et's or hp... because it evens out. The rotating weight loss is equalled out from the steels weight creating more momentum?

Food for thought.

TransAm12sec

The flywheel is spinning at a considerably higher rpm compared to the driveshaft, until the transmission is in the 1:1 ratio gear.

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iTrader: (17)

true, but it is still possible though.... Never said it was fact just a thought.

83 Crossfire TA

iTrader: (2)

3 issues (besides the fact that I have a blinding headache and can’t think):
- there is something called the radius of gyration, or the radius of from the axis of rotation that you can represent the whole mass of the rotating item being at WRT to it’s moment of inertia. Yes, a driveshaft has a radius of gyration of almost it’s diameter since it is a tube and most of it’s mass is at it’s outside wall, but of course, a flywheel is usually 12” or so around so no matter what it’s radius of gyration is further out. The Moment of inerta (how much inertia a rotating item stores) is proportionate to the ^2 of the radius, so a small difference in diameter makes a big difference in the stored energy.
- even if it wasn’t or the radius, a typical flywheel/clutch/pressure plate… assembly is MUCH heavier then a driveshaft. An LT1 f-body stock assembly weighs 38#, a typical “performance” driveshaft will be in the 3-8# range.
- even if it wasn’t for the radius and the weight, the fact is what you’re talking about is basically an old racer’s myth. There has been a bunch of testing of this done recently, comparing some of the super light weight aluminum assemblies with the billet, and OEM steel/iron assemblies, and every test that I’ve seen has shown that lighter assemblies go faster at the dragstrip, rev faster so are more responsive on the road course…

The reason to have a higher rotating inertia is that as long as you stay away from critical speeds it smoothes things out. A heavier flywheel assembly is probably the one biggest things that you can do to making a smoother idle… as a matter of fact, a lot of heavy trucks that may see extreme loading come with extremely heavy flywheels, and some of the 4x4/crawler guys use 90lb or so flywheels just so if they have to they can idle down/load down to an extremely low rpm without stalling.

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iTrader: (17)

Not to get off subject, but what U joints you guys think works well with the stock steel... I need to rebuild by shaft. Also, who can balance my driveshaft?

83 Crossfire TA

iTrader: (2)

they all pretty much work the same. the ones not drilled for zerks are stronger but I've never heard of someone breaking a u-joint before breaking the acutal DS...

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iTrader: (17)

That's good to know. I rather have a zerk fitting.

bgmoss

I am thinking about replacing my steel driveshaft in my 89 formula 350 as well to correct a 85-90mph vibration. I called the local yard looking for a driveshaft from a 98 z28. They said there are two options:

3.23 ratio or w/o 3.23 ratio. I can get either.

What is the difference between the two and which one is the preferred one to get for my swap?

thanks

TransAm12sec

This is off the top of my head, but some 2.73 gears may have had steel driveshafts. Do not quote me however.

metalic5

wow.... any one of you guys ever heard of harmonics?
cuz you all say how a steel vibrates at higher speed, well that vibration throws off the harmonics, which will decrease hp. don't believe me, go get a lathe put a metal tube on the and turn the lathe on if its balanced perfectly then it will run smooth and take less time to get up to speed with out damaging anything. if you put it on a little bit off center it will vibrate and take longer to get up to speed. an aluminum drive shaft just becuase its balanced will raise hp at the wheels, and the fact that its easier to spin it will also increase hp to the wheels. we tried it on my buddies T/A it ran the same ET but it ran something like 2 or 3 mph faster. when you start putting some real power down it will make more of a difference. in my opinion yes $125 to $150 is worth it for an aluminum drive shaft. its nicer, last longer, runs smoother, is lighter, and puts more power to the wheels.

one more thing if it doesnt make a difference between steel and aluminum, then GM would have kept it steel and saved the money, cuz aluminumn isnt cheaper then steel. just think about that.

83 Crossfire TA

iTrader: (2)

Um… yea… sure.

The answer is harmonics, but the rest of what you’re talking about no one knows. Yea, aluminum has a higher harmonic frequency then steel, which means that the speed where the driveshaft will be prone to naturally vibrate will be higher.

The thing with a drive shaft with a u-joint at either end is that because of the angle that the u-joint flexes even at a steady speed the actual driveshaft accelerates and decelerates as it spins. At the harmonic frequency of the shaft it will naturally flex it’s greatest distance, and that acceleration and deceleration amplifies that flexing. When the shaft flexes then obviously, the shaft becomes imbalanced in the direction that it’s flexing, causing a vibration.

westman

So should I spend the $100 or not? lol

Gramps

iTrader: (1)

haha go for it dude. it offers better balancing, less rotational mass, and doesnt flex like steel shafts will. an ali shaft is more responsive because it wont be prone to twisting, unlike a steel shaft.

plus its only 100 buks, and when you tell your friends "its got an ali driveshaft!" they will be pretty impressed...its all about pleasing the pesants.

vorgath

Plus it'll look nice no more rusty looking shaft.

Gallileo60

UH YES.............................