Tell you what...I'll do the long term testing of CF with my car. When it explodes, I'll let you know.

 

And while this article might fall under the BS marketing category as well, it actually has some very good information in it on torsional spring rates and such.

http://www.acpt.com/article1.html

And for what it's worth, when I ordered my carbon fiber driveshaft, Precision Shaft Technologies actually tried to talk me out of it due to its expense. They said something to the effect of "Passenger cars with your power usually get a good aluminum shaft, and that's all they need. People only go with Carbon Fiber when they can't get a steel shaft made that will hold the power." I was looking for the vibration damping more than anything, which is why I ordered it. My 4.11s (if I ever get my rear installed) are gonna cause this DS to spin more while cruising, and I didn't want the vibration.

 

And a little snippet from the Mark Williams website:

http://www.markwilliams.com/driveshafts.aspx

The one con for carbon fiber is the possibility of road damage from flying debris, and that was a risk I was aware of and willing to take.

 

Thats what I thought

 

Mines aluminum and with so many saying theirs are too maybe just maybe you COULD be wrong. Believe they come with the GU5 Rpo code for the a4's. I don't research M6s as I do not own one.

 

Haha, ok guys. Lets all just grab a magnet, crawl under our cars, and see who's d*ck is biggest!

 

The main attraction to CF is its light weight and characteristics under "shock"
It will have a lot more "spring" to it than other materials and will dampen the shock on the rear end a tad. Also, if you DO drop the shaft on a hard shift instead of vaulting you (no shaft loop...) or beating the ****! (shaft loop) out of the underside of your car, it will just shatter into a million pieces kindof like a piece of bamboo. MUCH nicer imho. NO where NEAR optimum, but not as bad as steel/aluminum by a long shot!

 

Do I win if mine prevents me from getting under the car or does that mean I am disqualified?

PS, mine is aluminum and I dont need a magnet to confirm it.

 

Lmao, nice one, I guess if your he only one...if not then we'll all have to start measuring how tall our cars are from the ground...

 

You can buy steel shafts to 2500+hp. I wouldn;t call that weak. Secondly if you think carbon fiber is an idea shaft material so be it. elastic deformation over time will fail and shaft and in that orders its cf,aluminum,chromoly,steel. whilst a aluminum or CF shaft looks like a great deal at the outset its not. and while the fibers in Cf are stronger per lb then steel the issue is not the fibers its the bonding resins. -

 

So what you are talking about is a manufacturing defect...would you like to provide names of manufacturers that can't make a CF driveshaft to save their life? I really want to see some hard data on this one, because you are speaking in generalities about something that is very specific.

And what's the outer diameter on the steel shaft that supports 2500+ HP? Just curious...

 

Ill second this...

I just happened to goto high school with an Editor at large for Turbo... and the claim was laid from an all wheel drive rice patty. Not a single shaft RWD F-body. Half the shafts used.. @ 2.5hp maybe ?? Yeah, ok. Its not really a "gain"... as it is more of just freeing up what is already there.

And FWIW, the only real benifit I can attributes to running a CF shaft is in shifting (espically down shifting) and reduced harmonics. The harmonics part pretty much speaks for itself, but for those that dont get it... reduced harmonics = much increased durability over the life of the part. This even means reduced harmonics being transfered to the rearend/differential which improves bearing life, for lack of a better example.

One of the biggest factors that is underlooked and misunderstood is what really happends to the shaft when it does fail. Yes, my biggest move to a CF shaft is the saftey factor first, and... reduced mass and harmonics second. When the shaft does let go, it doesnt upset the chassis and spin it around 180 when it unloads. The CF shafts dispersed energy goes into the shaft basically blowing it up and releasing its mechanical energy through that operation. A steel or alloy shaft... isnt quite that lucky. I have seen numerous 180's (on the freeway no less) when shafts failed... not to mention beating the hell out of the bottom of the chassis itself.

As for other various issues, some probable - some not... the whole resin issue is kinda mute as it has been offered here. The resin issue was something from over ten years ago, right next to the bonding epoxy issues related to yoke attachment. I guess you could say I have a little experience with this very subject... as I have been using CF shafts for 13+ years in various racing facet's. The shafts of new, Mark Williams and ACPT specifically, no longer have the issues of the old. And if you think that CF shafts dont live up to impact loading, let me just bring up offshore boat racing as something that will put that issue to rest forever. OS racing puts more impact loading into a shaft than any other use for a CF shaft made. Not that I am an expert in this subject or anything....

I am not however, one that is sold on and will only use CF shafts... as I use moly, 1020 DOM and Duraclan, depending on application. From shaft diameters as small as 2" all the way up to 4.5"... but the material selection does have a great deal to with the shafts critical speed. Like I said, it depends on application.


That's too damn funny... I was just about to ask the very same question.

 

I thought that the higher gear ratio rear ends came with aluminum rears. Like the GU5 option mine had, 3.23 rear, aluminum shaft. i think the 3.42's in a M6 came with them too.

Back to the topic, I was going to buy an CF. If it breaks no big deal. I've seen steel shafts break and cause damage even with a loop. Oh yeah... and CF shafts are smooth at high speeds. +1

 

Well...the durability test continues on my car. Still daily driven, still driven hard. And currently undergoing corrosion testing as the county decided to salt the hell out of everything paved during the last snow episode.

 

The fbody aluminum driveshafts are good but have seen them twist with Nitrous on drag radials.

I'm going carbon fiber in my GTO, not quite for power gain, but GTOs have vibration issues with 1 pieace driveshafts over 120mph+.

 

A nice chromoly steel driveshaft would be my choice, it's a nice balance of strength/cost. I would stay away from aluminum as it has no fatigue limit and will EVENTUALLY break as it continually is getting weaker everytime a force is applied to it. I would stay away from CF as well, I think it has been covered decently enough in previous posts in this thread.

 

As far as tensile strength goes yes carbon fiber is 10 times stronger than steel. But since a drive shaft is not subjected to tensile strength it is subjected to torsional strength in which carbons strength goes WAY down. If you wanted i could give some numbers but if it were me i would be going with a chrome moly ds rather than steel. its as light weight as aluminum but stronger than steel. But thats my personal choice

 

my 99 A4 has a stock aluminum DS. IRRC CF is much harder than steel pound for pound, the parasitic loss from metal driveshafts will be reduced with CF, how ever there will be a negligable amount of low end torque loss. The gains from a CF will probly be noticeable on these cars but nothing spectacular. My 240sx had a 3 piece steel driveshaft stock and ended with a cf one later on lost about 20lbs of rotating assembly wieght huge gains.
not sure what the weight diff between Fbody driveshafts are.

 

My 3.75" carbon fiber driveshaft weighed in at 12 lbs with a powerglide slip yoke up front, and 1350 u-joints. The stock aluminum shaft out of my car also weighed 12 lbs, but it uses Saginaw 3R joints instead. No gain on mine, but the strength of the carbon fiber shaft over the factory aluminum piece is substantial.

That said, the weight savings with a driveshaft wouldn't amount to much in the way of inertial mass since the mass is all fairly close in to the axis of rotation. My 20 lbs saved on my clutch/pressure plate/flywheel setup was a very noticable difference, and I'm guessing that was due to the diameter of those parts (inertial savings were much more).

 

I don't know if anyone has cleared this up 100% or not, so here is the correct info...

ALL m6 cars have alum drive-shafts, ALL a4 cars that came factory with 3.23s have alum drive-shafts. The only f-bods to have a steel shaft would be the autos with 2.73s.