Aluminum driveline.

[NikFu S.]

Originally Posted by svxsubaru1

I have to aggre the idea of spending at least probley $500 if not more for about 1 hp, and 10 pounds seems bad for a peformance gain, money ratio.

Where are you getting these numbers? You think it would only drop ten pounds?

Anything that will release some of the torsional stress on the drivetrain is worth the money in my eyes.

[svxsubaru1]

Originally Posted by NikFu S.

Where are you getting these numbers? You think it would only drop ten pounds?

Anything that will release some of the torsional stress on the drivetrain is worth the money in my eyes.

Well the stock pice dosent weight that much, 20-30 pounds. And i never have heard of them really blowing up, even with WRXs putting out over 400 hp, so at least there strong enough. I am not against it, i just don't think there a good idea for a person that has a good stock drive shaft and is looking to ditch it for a aluminum one of questionable quality, and strenght for very minimal gains.

[NikFu S.]

Originally Posted by svxsubaru1

Well the stock pice dosent weight that much, 20-30 pounds. And i never have heard of them really blowing up, even with WRXs putting out over 400 hp, so at least there strong enough. I am not against it, i just don't think there a good idea for a person that has a good stock drive shaft and is looking to ditch it for a aluminum one of questionable quality, and strenght for very minimal gains.

I figured they weighed more in the range of 50-60. Regardless I'm going to see what I can find out come Monday.

[Chiketkd]

Originally Posted by svxsubaru1

Well the stock pice dosent weight that much, 20-30 pounds.

I've had my factory driveshaft off twice during two trans swaps, and I would estimate that it weighs somewhere in the 30-35lb range. It's definitely very strong and robust in design.



-Chike

P.S. While a slightly lighter weight, one-piece aluminum driveshaft would be nice, I'm wary of switching to an aftermarket piece due to safety reasons. If you've ever held the stock unit, you'd realize that it has been precisely balanced to eliminate harmonic vibrations in the high rpm ranges - most aftermarket companies don't have a quarter of the R&D $$$ invested into their driveshafts that OE manufacturers put into theirs. This is another reason why you wouldn't see an under-drive pulley listed in my mods.

[WGJ]

we can always count on you to contribute sound reasoning to any discussion.
While the idea of lightening components has an obvious appeal for me, I never considered the issue of vibration. For me, that's v. important because I really like and appreciate the inherent smootheness of the flat six engine and driveline. It's a major contributor to the SVX's quietness.
WGJ

[TomsSVX]

my main interest lies in the replacement of a broken part though. Say my center bearing craps out or the universal joints fail....It would probobly be cheaper for me to invest in a lightweight one peice rather than a new oem or lengthen my spare. I am curious, not bent on getting one a I have many other mods for my car listed up pretty well.

Tom

[NikFu S.]

If it only weighs 35 lbs at most I'm not going to worry about it. I figured the thing was a massive cylindrical hunk of gargantuan steel.

Where the heck is all the weight in this car?

First, I strongly doubt that Chevrolet ever used Carbon fiber for a stock driveshaft in a pickup truck, CF's only advantage over aluminum is only *slightly* less mass, and the way it breaks. Many ultra-high power drag & race cars use CF as a driveshaft material because when it breaks it doesn't pole vault the car, it just shreds itself into dust.

Many MK3 Supra owners are ditching the stock driveshaft (around 35lbs) and replacing it with one piece aluminum units that often weigh around 11-12 lbs. There have been no failures reported and the engine response gained from dropping over 20 lbs from the rotating mass of the drivetrain is easily equal to if not more of a gain than doing an underdrive crank pulley and a lightweight flywheel. The improvement in engine response while in gear is well worth the effort and money. Naturally it would be smart to have a driveshaft loop made to prevent the car from getting vaulted if for any reason it failed, but I doubt that a quality unit would ever fail at the power levels any SVX could be expecting to make.
A aluminum driveshaft is vastly favored for Supras over a crank pulley because the crank pulley is of even greater significance in an inline 6 such as the supra because the crank is twice as long and has vastly more vibration for the crank dampener to help abate. A flat 6 design would be much less sensitive to losing that dampening.

Beyond that, the mass of the driveshaft and the presence of its carrier bearing is due to NVH purposes (Noise, Vibration, Harshness). Segmenting the driveshaft makes it quieter and makes the driveshaft require much less exact balancing procedures. An aluminum driveshaft may make the drivetrain slightly more noisy at highway speeds but with how much insulation the SVX has I doubt anyone would notice, particularly in the wake of how much more responsive and fun the car would be.
Furthermore, balancing a driveshaft properly can be done at any driveshaft shop, and I've never seen a stock driveshaft that didn't have little balance weights welded to the surface of the shaft somewhere.

[NikFu S.]

And then BAM! knowledge flies out.


Haha, ok, you are reaffirming what my friend is ranting about. I'll know something come Monday evening.

[TomsSVX]

Originally Posted by Wreckless

First, I strongly doubt that Chevrolet ever used Carbon fiber for a stock driveshaft in a pickup truck, CF's only advantage over aluminum is only *slightly* less mass,

No offense but GM did use these in their trucks... If there is one thing I know about, it is 88-98 model gm pickups as i did mine, my father's and my buddy's work and dropping transmisions was my job. Those things weighed liek 10lbs at most and they were about 5-6 feet long

Tom

[mbtoloczko]

Originally Posted by Wreckless

...
Beyond that, the mass of the driveshaft and the presence of its carrier bearing is due to NVH purposes (Noise, Vibration, Harshness). Segmenting the driveshaft makes it quieter and makes the driveshaft require much less exact balancing procedures. An aluminum driveshaft may make the drivetrain slightly more noisy at highway speeds but with how much insulation the SVX has I doubt anyone would notice, particularly in the wake of how much more responsive and fun the car would be. ....

Besides NVH, a one-piece driveshaft would not work well on an SVX because the output shaft angle on the tranny and the pinion shaft angle in the rear diff angle are not matched for a one piece driveshaft. I've measured the angles, and the only thing that will work is a two-piece driveshaft. A one-piece driveshaft would vibrate badly at freeway speeds and above (regardless of how well balanced the driveshaft might be). Now that I think about it though, I guess if you wanted to shim the rear diff, you might be able to adequately match up the angles. But then it comes down to whether there would be any real benefit to a one-piece driveshaft. If you were replacing a worn driveshaft that was vibrating badly, it might be worth it, but otherwise, I'd spend the money on tires/wheels/suspension/exhaust.

Originally Posted by tomssvx

No offense but GM did use these in their trucks... If there is one thing I know about, it is 88-98 model gm pickups as i did mine, my father's and my buddy's work and dropping transmisions was my job. Those things weighed liek 10lbs at most and they were about 5-6 feet long

Tom

If one did something like

Originally Posted by tomssvx

... break at the front yoke and drop down only to lift the back of the truck up and almost flip him over doing 60mph

then it wasn't a carbon fiber driveshaft. Period.

However, I did some quick research of my own and found that in 1988 GM started using a one piece driveshaft of "fiberglass reinforced vinyl ester pultruded over an aluminum tube" (from the strongwell website) which would be fantastically light and being that it was built over an alumnium tube that explains how it would still pole vault a truck that had a yoke failure, as a true CF driveshaft would not, it would just crumble and break.

Cheers for keeping me honest

As for the output shaft angles, how much of an angle is it? The MK3 Supra's is far from perfect either (somewhere around 11 degrees) and people have relied on the two U joints at the diff and the output shaft without incident.

[TomsSVX]

well in any sense it had the same pattern as carbon fiber does and I know GM wouldn't have made these to just look like CF. So i guess I was wrong in that respect.

Tom

From the strongwell website:

Strongwell developed new pultrusion equipment and technology to produce the Spicer Graph LiteTM design. A composite of fiberglass, graphite and a special resin is pultruded directly onto the seamless aluminum tube. This composite reinforces the tube, eliminating the need for center bearings. The composite is engineered with an isolation barrier between the aluminum tube and the graphite to eliminate electrolytic galvanic corrosion.

graphite reinforced fiberglass would look and awful lot like carbon fiber I think.

[mbtoloczko]

Originally Posted by Wreckless

...

As for the output shaft angles, how much of an angle is it? The MK3 Supra's is far from perfect either (somewhere around 11 degrees) and people have relied on the two U joints at the diff and the output shaft without incident.

I don't have the numbers in front of me. Yeah, using a double cardan at both ends of the driveshaft would solve the angle problem.