steel vs. aluminum drive-shaft (revisited)

[monterey1962]

Searched and found outdated info.

Are there any updated benefits or issues with the steel-to-aluminum drive-shaft swap? (Yes, I know you have to change the flange.)

If you were to spend a fair amount of time at the 1/4 mile drag strip, which drive-shaft would you say is better? Will the aluminum hold up just as well as the steel?

All relevant info is appreciated.

[gadget73]

The only thing I can tell you about the aluminum is that they tend to vibrate less, though in the 1/4 I highly doubt that matters any. I have heard it postulated that the reduced mass of the aluminum shaft gives you a slight advantage with acceleration by reducing the amount of rotating mass in the driveline that must be accelerated, however I don't know if thats BS or reality. It sounds like it makes sense, but I'm no engineer.

[91grandmarquis]

That should work because there will be less mass to get moving, However would you notice it? I have no idea. I honestly would have to figure out the forces required to start each in motion based off of there individual weights, and I haven't the least idea were to start with that, However im guessing i would need to go from rotations to radians a second yada yada, throw in some force equations and vector projections and bada bing. I can't wait for college.

[Grand Marquis GT]

You can polish an Aluminum D/S easy.

[Southern_Pride]

The difference in weight is not much. I run one but only because I had one laying around and my low gears. I never really noticed any difference between the two.

[5.0turbines]

I have a 99 aluminum driveshaft. gonna make a thread about it as soon as I drop the steel shaft for comparison. here's what it weights. BTW my digital scale loves to lie to me +/- 5 pounds. sometimes it weights 17lbs.

[monterey1962]

Somewhat off track, but ...

If one were to change over to the aluminum drive shaft, could a person get away without installing a new crush sleeve when swapping yolks? Could the pinion nut be tightened down, then just test the pre-load?

[Lincolnmania]

no need to change the flange justin........use the yokes from your stock driveshaft and two conversion u-joints......i saved the flap from the box, the part number for the combination universal joint is 1-0134
i just googles that number just to verify that it is valid.........i had a spicer number that crossed over to this number but i cant remember for sure the number.

[Lincolnmania]

found the number 5-134x
either of those numbers should work
we used these u joints with a 97 pi shaft on toms vic

[P72Ford]

That should work because there will be less mass to get moving, However would you notice it? I have no idea. I honestly would have to figure out the forces required to start each in motion based off of there individual weights, and I haven't the least idea were to start with that, However im guessing i would need to go from rotations to radians a second yada yada, throw in some force equations and vector projections and bada bing. I can't wait for college.

To gain a better understanding of how aluminum will compare to steel, all you really have to do is compare the moment of inertia (or mass moment of inertia) of the cross section of a steel shaft to that of the aluminum shaft.

That will shed some light on the ability of the cross section to "roll". In other words, if you cut a 2 inch wide section out of each shaft, and set them on an incline; the one that rolls down the incline first has a lower moment of inertia. An aluminum driveshaft more than likely has a larger wall thickness, and a larger diameter, which will increase the moment of inertia, if weight was being neglected.

Theres no need to do all kinds of crazy math about the force required. If the mass moment of inertia is lower, it will rotate about its central axis with a lower force application, which is all that really matters. If an aluminum driveshaft has a lower mass moment of inertia, it is worth running.

http://www.vectorsite.net/tpecp_04_05.png

You could use either of the first two situations. If you use the first, you are neglecting the wall thickness; I'd use the second.

[Pirate]

To gain a better understanding of how aluminum will compare to steel, all you really have to do is compare the moment of inertia (or mass moment of inertia) of the cross section of a steel shaft to that of the aluminum shaft.

That will shed some light on the ability of the cross section to "roll". In other words, if you cut a 2 inch wide section out of each shaft, and set them on an incline; the one that rolls down the incline first has a lower moment of inertia. An aluminum driveshaft more than likely has a larger wall thickness, and a larger diameter, which will increase the moment of inertia, if weight was being neglected.

Theres no need to do all kinds of crazy math about the force required. If the mass moment of inertia is lower, it will rotate about its central axis with a lower force application, which is all that really matters. If an aluminum driveshaft has a lower mass moment of inertia, it is worth running.

http://www.vectorsite.net/tpecp_04_05.png

You could use either of the first two situations. If you use the first, you are neglecting the wall thickness; I'd use the second.

Nerd.

[P72Ford]

Nerd.

Damn right. Nerdiest nerd of all the nerds.

I can live with that.

The important question is, did it make sense? Sometimes I have a hard time putting stuff into words so that it can be understood.

[Pirate]

Damn right. Nerdiest nerd of all the nerds.

I can live with that.

The important question is, did it make sense? Sometimes I have a hard time putting stuff into words so that it can be understood.

It was rather presentable, my dear Watson. Rather presentable.

I got lost for a moment, but while I love the pursuit of science and math, I find that while I can grasp the theory behind most...uh....theories....implementation has always been a problem of mine, not to mention understanding most 'sciencenese'. It seems like my chosen 'technical' field is more that of a psychological bent, wondering more about what lays behind the pursuit of such topics than said topics themselves.

The typo has been repaired, btw.

[monterey1962]

no need to change the flange justin........use the yokes from your stock driveshaft and two conversion u-joints......i saved the flap from the box, the part number for the combination universal joint is 1-0134
i just googles that number just to verify that it is valid.........i had a spicer number that crossed over to this number but i cant remember for sure the number.

found the number 5-134x
either of those numbers should work
we used these u joints with a 97 pi shaft on toms vic

Cool. I'm assuming it's the same part #'s to use towards the '90/'91 aluminum drive-shaft. Also, I wouldn't have to change the yolk at the transmission end 'cause that end will install on the trans tail shaft as any other DS would, correct? Just run one conversion u-joint at the differential end.

5134x ...
Napa site lists a Spicer u-joint for $23. LINK
Summit lists it for $43 ... ouch. LINK

Please correct me if I am wrong. Reason I bring this up is ... the '90 here is wrecked and has the aluminum DS, and my '88 has the steel DS. '88 will be getting 4.10's soon. I don't want to rip the yolk (differential end) off the '90 if I run the risk of messing up pinion bearing load. I'm driving the '90 for work and need to keep it on the road.

[Lincolnmania]

i got them for much less at autozone, but i dont know if you have autozone out there......check online....saw them for 17 ea