Aluminum vs steel driveshaft.

My complete drive train is new. The last item to be replaced was the drive shaft, since I had vibration above 80, and very bad above 90. I installed a aluminum drive shaft last month, and it is as smooth as silk. My aluminum one is 9 lbs lighter than the factory steel one. It looks nice also.

They probably have a better balance than the factory shafts. Whataya think? Are they a larger diameter? Do they need to have a better balance?

Let me requalify - get any steel shaft that has not been custom balanced - custom balanced with a gear change.

Ahhh... since this is a thread full of folks talking from their rear ends... I think that I wold like to do the same.... Here's how it was explained to me....

The FMS aluminum DS (overall) is slightly stronger than the stock piece. The aluminum is more rigid meaning that it changes shape a LOT less during it's life. The problem is that when it DOES change shape then that's it. It's over, ca-put, scrap, whereas the steel drive shaft is considerably more flexible and will/does change shape thousands of times during the course of extreme duty (even normal duty for that matter). Not a problem until metal fatigue starts to set in (dependant on how often it's put in that condition).

So... though there's not a HUGE difference in strength between the units, the durability factor for modified cars is supposed to be greatly improved with an aluminum DS. The number of instances where "It's been fine all this time until one day... SNAP!" are supposed to be reduced by using material that keeps it's shape right up to containing enough force to destroy it completely.

I'd love to see how many people HAVE them that rip on them...lol Whoever said aluminum flexes...get your facts straight. Aluminum is more rigid than steel, which reduces flex and drivetrain vibration. Aluminum requires less weight to balance, which also adds (subtracts?) to the weight difference. The FMS shaft is tubular, which also adds to weight loss. The yokes are beefed up to assist in durability. I know guys pushing 600+ who do 5k clutch drops on slicks who aren't even TESTING how strong these shafts are. You guys need to think physics for a second...you really think an aircraft grade tubular aluminum shaft is going to twist BEFORE the universals blow out? Everything has a weak link, and that's usually where you want it when it comes to a drive shaft. Steel on the other hand, flexes too much, vibrates too much, and as someone else said i've seen them twist like a twizler and fly out from under a car looking like a chewed up straw. You'll see universals blow out before you twist an aluminum shaft. If that scares you, then decide one of two things... A) does my mostly stock and/or bolt on Mustang make enough power to actually blow apart that universal? and B) if yes, then you probably should have already invested in a driveshaft safety loop, and it won't matter what your shaft is made of because you're going to be busting universals all day anyways.

On a side note....do any of you think Ferrari uses steel drive shafts?

Uhhh guys, no need to be retarded, steel is far more rigded than Al. Mild low carbon steel (something like 1020) has an modulus of elastisity of around 30,000 KSI, and 6061T6 is around 10,000. That means Steel is 3 time more ridged.

as for Fatiuge stregth around 15,000KSI for 60601T6 and 100,000 for mild steel, so you can do a ton more clutch drops with steel

keep in mind this is just material properties, There are many other factors that affect the ultimite streagth of a driveshaft, but lets get our facts strait before we dive into those.

a Alumium driveshaft has to be larger diameter to keep streagth up, becasue the larger dia spreads out the hoop stress (the fundamental reason you twist up a driveshaft)

HISSIN50 is dead on about the increase in diameter of an AL driveshaft affecting rotational inertia. Does the decrease in weight of the Al shaft cancel out the increase on roational interia from the increased diameter? I don't know, but one of us should really test it.

bock said:

My real problem is vibration

I have tried 2 different DS and it still vibrate.

Feel like coming from the rear end...

really vibrate from 75-80 mph and up... in gear or not...

Click to expand...

I have an idea, get your tires balanced.

My car had 4.10's in it when i got it with the stock ds and had an annoying vibration at highway speeds. I just put an aluminum one in yesterday and it completely solved the problem.

Ford says somewhere how much stronger the Aluminum piece is over the stocker. My stock ds was a complete pile of ****. I couldnt believe how much lighter and nicer the AL piece was when i got it. My car is also smooth as silk with it. the u joints the AL piece comes with are also very high quality.
And whoever said their AL Driveshaft is rubbing thier emergency break brackets....damn bud. I was just under there sat changing the gears to 327's (much better than the 355's IMO...another story), and thats quite a bit of distance to be traveling, i would fix that pronto before you junk both your ds and brackets. but i do see where you are talking about. stinks man...

Anyone think the move to a AL drive shaft making things smoother might be due to a better balance? Try putting in new joints and balancing a steel shaft and see what happens. yeesh......

well no kidding, im not trying to set the world on fire here. its a nice piece and was in the budget, looks better, and is stronger. obviously the smoother ride is from correct balance, but put the two side by side and its a no brainer.

for a DD

If my steel driveshaft "looked better" I would put it back on...in my case it didn't do anything...I guess it was balanced well enough.

my caprice driveshaft broke like a pepsi can twisting and shredding right in the middle , steel, but rusty , let me see if i can get you guys the pic.

link