Why an alum. driveshaft?

Posted By: rod440

Why an alum. driveshaft? - 09/20/11 03:28 PM

I need to have a driveshaft made for a 440/4 speed Duster that I've been working on.What is the advantage of using aluminum instead of steel? Many newer cars & light trucks use aluminum shafts so there must something to it.I read about a dyno comparison between alum. & steel shafts & they claimed that with the alum shaft the car made 10 more HP at the wheels! I'm skeptical about this ,but if the OEM's use alum. then maybe there's something to it? Any opinions or experience on / with aluminum driveshafts?

Posted By: AndyF

Re: Why an alum. driveshaft? - 09/20/11 03:49 PM

Aluminum allows you to get a higher critical speed without adding any weight. If that doesn't make any then you probably don't need an aluminum driveshaft.

Posted By: Fury Fan

Re: Why an alum. driveshaft? - 09/20/11 04:16 PM

I don't remember teh formulas, but weight savings from a rotating object is worth more than just the weight reduction.

Meaning - 10 lbs saved on teh driveshaft removes 10 lbs from teh car, but it also is easier for the engien to spin it. As AndyF mentioned, the lighter weight allows you to make a larger-diameter/stronger shaft.

By weight, aluminum is stronger than steel.

Posted By: pishta

Re: Why an alum. driveshaft? - 09/20/11 04:20 PM

Weight and mass. Less mass equals less power to spin, less weight means the motor works less to keep the vehicle at the same speed , acceleration is also improved. Cost and manufacturing may be less with AL also. 95% of the time its the bottom line that is affected.

Posted By: RapidRobert

Re: Why an alum. driveshaft? - 09/20/11 04:37 PM

Good: Would save a fair amount of weight. Hype: wouldn't take 10 less horsepower to rotate it as opposed to a steel one

Posted By: POS Dakota

Re: Why an alum. driveshaft? - 09/20/11 06:14 PM

What about the ability to flex more before breakage?

I had a driveshaft made for my truck...75.5 inch center to center between the front and rear joints. It's 5 inch diameter tube.
All aluminum. it's definitely light for it's size and is supposed to be very strong.

I was told it couldnt be made of chromoly, but I dont know what the reasoning was.

Posted By: autoxcuda

Re: Why an alum. driveshaft? - 09/20/11 06:32 PM

Quote:

What about the ability to flex more before breakage?

..

I remember hearing from someone on a Craftsman Truck Series team that they found their lightweight driveshafts were whipping/flexing on the chassis dyno. That flexing cost HP. So you can go too light, not cause breakage, but not gain the HP you 'think' you should.

Posted By: Stanton

Re: Why an alum. driveshaft? - 09/20/11 06:57 PM

There are loads of aluminum driveshafts kicking around in the wreckers. It would be nice to know if any use the same front and/or rear u-joints as a Mopar - then all that would be necessary would be to shorten it.

Also, what diameter would be necessary to provide the same or more strength than a stocker?

Posted By: savoy64

Re: Why an alum. driveshaft? - 09/20/11 08:01 PM

i picked up an aluminum driveshaft from a 96? dodge van at the pickapart--had it shortened ($100) and run it under my 64---bob

Posted By: Darryls-Demon

Re: Why an alum. driveshaft? - 09/20/11 08:29 PM

The big reason I went with an alum drive shaft was cost, I found a brand new one out of a 3/4 ton ford van with new 1350 U joints on Craigslist for 50 dollars. 125.00 to have it shorted.

Posted By: Challenger 1

Re: Why an alum. driveshaft? - 09/20/11 11:22 PM

Why not?
I called my local drive line shop and asked for prices both ways, steel and aluminum for my 71 challenger. Aluminum cost about the same as I remember or a little more.
The new aluminum one does not turn down like a stocker does. Here's a picture of it. They had it ready to pickup the next day. It has fit and performed fine in my 440/6 challenger. The TTI mufflers clear too luckily.

Posted By: Moparmick

Re: Why an alum. driveshaft? - 09/21/11 01:03 AM

Challenger, Where did you have your aluminum shaft made? friend of mine is looking into it for his aspen

Posted By: jcc

Re: Why an alum. driveshaft? - 09/21/11 01:34 AM

Quote:

The new aluminum one does not turn down like a stocker does. Here's a picture of it.

It's not clear to me if you are suggesting the lack of "turn down' makes for a stronger driveshaft. i don't know, but if one used a high tech axle shaft as an example, that down turn might be an engineering plus, or just an OEM move to save money.

Posted By: Challenger 1

Re: Why an alum. driveshaft? - 09/21/11 01:46 AM

Quote:

It's not clear to me if you are suggesting the lack of "turn down' makes for a stronger driveshaft. i don't know, but if one used a high tech axle shaft as an example, that down turn might be an engineering plus, or just an OEM move to save money.

I was only pointing it out. I have no idea if it's best or not?
When I first saw it I was worried about muffler clearance because of lack of turn down.
Thinking about it I'm sure it's cheaper. I bet if I ordered steel I would have got the same thing?
It fit's, it clears and don't vibrate for just 2-300 bucks in 2006 if I remember right? I would think a lighter drive shaft would be easier on trans tailshaft bushings and I'm always looking to save weight, always if I'm putting fuel in it.
I bet it could handle quite a bit on the strip.
Came from Cincinnat Driveline and Hydralics. Have known the owner for many years before he even started his own company from being in the truck repair business. He used to be in Northside working for someone else selling driveline stuff a long time ago. lol.

Cinti driveline

Posted By: Moparmick

Re: Why an alum. driveshaft? - 09/21/11 03:10 AM

Thanks for the link

Posted By: Pale_Roader

Re: Why an alum. driveshaft? - 09/21/11 10:46 AM

Quote:

i picked up an aluminum driveshaft from a 96? dodge van at the pickapart--had it shortened ($100) and run it under my 64---bob

I dont suppose the yoke will just slide into my 833 no issues will it...???

Does that have the larger 7290 U-joints...???

This would make things too easy. My 70 Challenger needs a shaft...