Two-piece driveshaft

JakeRobb · 07-19-2008, 03:14 PM

So I was looking at the technical cutaway renderings in the Gallery area.

In particular, this picture:

I'm pretty sure I see a two-piece driveshaft.

IIRC, the '04-06 GTO had a similar piece, and those guys had an awful time getting it to hold significant amounts of power. I read about some guys trying one-piece replacements and having major vibration issues.

Does anyone know what the reasoning behind a two-piece driveshaft is? Does it result in a more consistent pinion angle or something? Also, can anyone elaborate on the issues it had in the GTO?

4THGEN Z · 07-19-2008, 07:42 PM

Isn't that a V6 drivetrain? The 4th gen V6 had a 2-piece DS as well.

bossco · 07-19-2008, 11:55 PM

Gahhhh... well at least the F5 crowd will be able to get in on the new millenium replacement for UD pullies. The 2-piece DS in the Mustang is a major horsepower soaker-upper.

Ron78Z&01SS · 07-20-2008, 12:17 AM

Looks like the V6 to me.

wbdigi.com · 08-16-2008, 03:35 PM

Isn't that a V6 drivetrain? The 4th gen V6 had a 2-piece DS as well.

shock6906 · 08-17-2008, 04:53 PM

Quote:

Originally Posted by wbdigi.com

Isn't that a V6 drivetrain? The 4th gen V6 had a 2-piece DS as well.

I don't see why it matters. A two piece driveshaft sucks whether it's a V6 or a V8. My V6 has a 1 piece Z28 driveshaft now. If the one piece works without any other modification to the car, then what's the point? Certainly a once piece driveshaft must be easier and cheaper to engineer and produce. I can't see any reason to have a two piece if a one piece will work.

JakeRobb · 08-18-2008, 11:00 AM

Quote:

Originally Posted by shock6906

I don't see why it matters. A two piece driveshaft sucks whether it's a V6 or a V8. My V6 has a 1 piece Z28 driveshaft now. If the one piece works without any other modification to the car, then what's the point? Certainly a once piece driveshaft must be easier and cheaper to engineer and produce. I can't see any reason to have a two piece if a one piece will work.

I think it helps to dampen vibrations.

shock6906 · 08-18-2008, 01:27 PM

Quote:

Originally Posted by JakeRobb

I think it helps to dampen vibrations.

As long as its balanced I'd imagine there wouldn't be too much problem. Yes, I know the steel one piece was a vibratin' mofo in many Camaros. The one I swapped into my V6 vibrates @ 55MPH. The one in my Z doesn't vibrate at all.

JakeRobb · 08-18-2008, 04:05 PM

Quote:

Originally Posted by shock6906

As long as its balanced I'd imagine there wouldn't be too much problem. Yes, I know the steel one piece was a vibratin' mofo in many Camaros. The one I swapped into my V6 vibrates @ 55MPH. The one in my Z doesn't vibrate at all.

I guess not so much in the area of vibrations you feel -- more of the high-frequency stuff that you can only hear.

ws6transam · 08-18-2008, 10:30 PM

A two-piece driveshaft with an intermediate bearing in the center enables you to have a higher critical speed rating on the driveshaft. Picture the driveshaft spinning at crazy-fast RPM's, then picture it starting to bend slightly in the middle, like a jump rope. The point where the driveshaft starts swinging like that jump rope is where the driveshaft reaches critical speed, and when that happens, you get vibrations galore, followed shortly by driveshaft failure. There are also oscillations at the harmonic frequencies associated with the critical speed RPM, and these are what you feel at lower speeds, such as 80 MPH+.

Engineers have to respect the driveshaft critical speed RPM when they design their drivetrain, and they try to move the critical speed RPM upwards by changing the diameter of the driveshaft, making it stiffer, or by making it shorter. The two-piece driveshaft is a method that is used to allow the driveshaft to spin faster with less oscillation. With the intermediate bearing, you in effect create a system of two smaller driveshafts, each of which have a higher critical speed than a long single driveshaft.

shock6906 · 08-19-2008, 05:02 PM

Quote:

Originally Posted by ws6transam

A two-piece driveshaft with an intermediate bearing in the center enables you to have a higher critical speed rating on the driveshaft. Picture the driveshaft spinning at crazy-fast RPM's, then picture it starting to bend slightly in the middle, like a jump rope. The point where the driveshaft starts swinging like that jump rope is where the driveshaft reaches critical speed, and when that happens, you get vibrations galore, followed shortly by driveshaft failure. There are also oscillations at the harmonic frequencies associated with the critical speed RPM, and these are what you feel at lower speeds, such as 80 MPH+.

Engineers have to respect the driveshaft critical speed RPM when they design their drivetrain, and they try to move the critical speed RPM upwards by changing the diameter of the driveshaft, making it stiffer, or by making it shorter. The two-piece driveshaft is a method that is used to allow the driveshaft to spin faster with less oscillation. With the intermediate bearing, you in effect create a system of two smaller driveshafts, each of which have a higher critical speed than a long single driveshaft.

Ah, my lesson for the day.

5thGen · 09-24-2008, 01:28 PM

IMHO it is a method that uses a trick that adds weight and complexity that can otherwise be done with better manufacturing techniques.

A high quality one piece aluminum shaft can be used, and after adding up the extra mount and bearings and joint, I wonder if it would be more expensive than 2 pieces in reality. I doubt it.

Regardless, I am sure some manufacturer out there will offer a one piece that will decrease powertrain loss and lower weight, both by a small margin.

diarmadhi · 09-24-2008, 02:19 PM

Quote:

Originally Posted by ws6transam

A two-piece driveshaft with an intermediate bearing in the center enables you to have a higher critical speed rating on the driveshaft. Picture the driveshaft spinning at crazy-fast RPM's, then picture it starting to bend slightly in the middle, like a jump rope. The point where the driveshaft starts swinging like that jump rope is where the driveshaft reaches critical speed, and when that happens, you get vibrations galore, followed shortly by driveshaft failure. There are also oscillations at the harmonic frequencies associated with the critical speed RPM, and these are what you feel at lower speeds, such as 80 MPH+.

Engineers have to respect the driveshaft critical speed RPM when they design their drivetrain, and they try to move the critical speed RPM upwards by changing the diameter of the driveshaft, making it stiffer, or by making it shorter. The two-piece driveshaft is a method that is used to allow the driveshaft to spin faster with less oscillation. With the intermediate bearing, you in effect create a system of two smaller driveshafts, each of which have a higher critical speed than a long single driveshaft.

These type of posts are exactly why I keep coming back here... Golden nuggets of information like this are worth it. I knew there was a purpose but to have the engineering answer to it is useful knowledge!

nelfastla · 10-25-2008, 02:38 PM

Quote:

Originally Posted by shock6906

I don't see why it matters. A two piece driveshaft sucks whether it's a V6 or a V8. My V6 has a 1 piece Z28 driveshaft now. If the one piece works without any other modification to the car, then what's the point? Certainly a once piece driveshaft must be easier and cheaper to engineer and produce. I can't see any reason to have a two piece if a one piece will work.

I´m gonna change the 2 piece drive shaft (the bearing has broken) of my 97 V6 for a 1 piece LT1 drive shaft. Does this work needs a heavy mod or something? Or the swap is just like that, easy. Just take out and put on.

JasonD · 10-25-2008, 07:25 PM

Quote:

Originally Posted by nelfastla

I´m gonna change the 2 piece drive shaft (the bearing has broken) of my 97 V6 for a 1 piece LT1 drive shaft. Does this work needs a heavy mod or something? Or the swap is just like that, easy. Just take out and put on.

Try the 1967-2002 Specific Technical Discussion / Drivetrain forum for that one.