Aluminum rear drive shaft

[fallguy]

Anyone??? What, why, from where and how much?

 

[DoubleDingo]

Would it have enough strength to withstand the torque being applied to it without twisting like a beer can?

 

[chengny]

http://www.dennysdriveshaft.com/c3_aluminum_6061_t6_driveshafts.html

 

[scottybaccus]

Driveshafts are so misunderstood.

In most instances, an aluminum shaft is a better choice than steel. For factory vehicles, it's less weight, less rotating mass, and just as durable as mild steel.

In my case, I opted for a 4" aluminum shaft because the longest mild steel shaft available would not meet my critical speed requirements. Critical speed is far more likely the cause of a shaft failure than brute strength.

Take any object and spin it at high speed. Centrifugal force tries to pull any material apart, like kids on a merry-go-round. Each type of tubing used in driveshaft construction has a critical speed; the limit of it's capability to resist these forces. The shorter the tube, and/or thicker the tubing wall, the higher the critical speed.
My stock shaft was about 56" long, 3" in diameter, .083 wall mild steel. I needed a 60.5" shaft. It was perfectly possible to re-tube my shaft, but using the stock diameter and wall thickness, the shaft would only be good to about 5800 rpm. With any OD transmission, it is entirely possible for any small-block to exceed that speed. My LS would potentially turn 6500 rpm, plus the OD ratio. I wanted an 8000 rpm shaft. The next step up was a 3.5", .083 wall, mild steel shaft, but it was only good to about 6300 rpm. That brings me to a 4" aluminum, .125 wall tube. Now I have a critical speed of about 7900 rpm. It was $550, all in. That's new youkes, joints and the slip yoke. If I was going faster, or with drastically higher power, I would want a thick wall chrome-moly tube. That means $$$$!

Before you decide on changing a shaft, you need to first ask what will be your max rpm, EVER? You only need to exceed critical speed one for it to fail. Not a sure thing, but...

 

[Skweegle89]

I had a dodge Dakota with a 360 in it that had an aluminum shaft. that thing was huge though. I have never heard of anybody twisting them off, but I suppose it could happen. I figure the rear end would go before the shaft.

 

[DoubleDingo]

Driveshafts are so misunderstood.

In most instances, an aluminum shaft is a better choice than steel. For factory vehicles, it's less weight, less rotating mass, and just as durable as mild steel.

In my case, I opted for a 4" aluminum shaft because the longest mild steel shaft available would not meet my critical speed requirements. Critical speed is far more likely the cause of a shaft failure than brute strength.

Take any object and spin it at high speed. Centrifugal force tries to pull any material apart, like kids on a merry-go-round. Each type of tubing used in driveshaft construction has a critical speed; the limit of it's capability to resist these forces. The shorter the tube, and/or thicker the tubing wall, the higher the critical speed.
My stock shaft was about 56" long, 3" in diameter, .083 wall mild steel. I needed a 60.5" shaft. It was perfectly possible to re-tube my shaft, but using the stock diameter and wall thickness, the shaft would only be good to about 5800 rpm. With any OD transmission, it is entirely possible for any small-block to exceed that speed. My LS would potentially turn 6500 rpm, plus the OD ratio. I wanted an 8000 rpm shaft. The next step up was a 3.5", .083 wall, mild steel shaft, but it was only good to about 6300 rpm. That brings me to a 4" aluminum, .125 wall tube. Now I have a critical speed of about 7900 rpm. It was $550, all in. That's new youkes, joints and the slip yoke. If I was going faster, or with drastically higher power, I would want a thick wall chrome-moly tube. That means $$$$!

Before you decide on changing a shaft, you need to first ask what will be your max rpm, EVER? You only need to exceed critical speed one for it to fail. Not a sure thing, but...

That is some good information, thanks posting that. I guess I have been living under a rock all these years because I have never heard of aluminum driveshafts.