INTENESS

iTrader: (4)

Well I picked up a the ACPT carbonfiber driveshaft fromk thunder racing about a yr ago.My car is 2001 ss 402 with 500rw on motor on 100 shot low 600's my car is a 6spd.Went to the track last weekened and on the first launch i'm on slicks by the way the driveshaft breaks about a foot from the rear end.This is with me dumping the clutch at 5grand.So fast foward to yesterday and same thing get new drive shaft from ACPT carbon fiber they replaced the other one with,I go to launch the car it hooks and boom bye bye driveshaft.Nowe I had the car at my speed shop the day before to make sure the pinioun angle was good they said it was set at negative 2.So what gives what is making these suposedly stong driveshafts break?Its been a expensive past tweo weekends for no run's man Im bumped carbonfiber

GMmexican

iTrader: (7)

well if it makes you feel any better after it breaks apart it turns into a giant broom....at least you can clean the garage.

on a serious note i would stay away from cf and get a chromemoly driveshaft from ls1speed.com

INTENESS

iTrader: (4)

TTT anyone got any idea why these supposedly strong driveshafts are breaking?

Black02SLPSS

iTrader: (5)

Because carbon fiber is much much stronger when a tensile stress is put on it. It is still very strong torsonally (twisting force) but its much better suited for applications where tensile stress is is an issue. But when you have a 500hp 402 stroker launching at 5grand your putting a shitload of shock load on it and that was enough to exceed the amount of torsion stress it can take.

INTENESS

iTrader: (4)

Thanx for explaining it to me,lesson learned expensive one too

BlackScreaminMachine

iTrader: (17)

Inteness, sorry to hear about the DS, I heard from JL about it. I saw the car last week at the shop, I was wondering why it was there.

That car has too much ***** for a carbon fiber, get a 3" denny's like me and be done with it.

NHRAFORMULA00

iTrader: (2)

TOO much HP at 600.Well my brother has a 62 Catalina with 950 HP running a CF drive shaft( 4 inch ) and he launches at 7500,liberty 4 speed! The shaft can handle the power,something is not right.Car runs 8.80s

chicane

I dont think that the above tensile strength example is quite up to par on this subject. And before everyone jumps onto the "Carbon Fiber shafts suck" bandwagon...

The very same shafts are used in offshore racing. With a few exceptions... the engines are 2000+hp blown big blocks (normally three to five engines), they weight three times the amount of your chassis weight and at 175mph its hard to keep them in the water with 9' swell's.

When you get one of these out of the water and the prop spins up... and then you pretty much slam the prop into something that is roughly as hard as running into cement... I dont believe that you can find anything with higher impact loading than that. A simple 600hp car leaving at 7500rpm doesnt even scratch the surface when comparing the impact loads.

So, lets nix that from the failure modes right up front, for now.

I have a question or two. Did the first shaft, and the subsequent second shaft, brake in the same place ?? Did it brake in the same way ?? Are there any witness marks down the TA that could lead you to think otherwise ??

Proper failure analysis is what will give you your answer. Speculation and oversight leads toward a post just like the way this one has started out.

INTENESS

iTrader: (4)

I know these driveshafts are rated for alot more hp then I have,As far as breaking they both broke in the same area about 8inches from the rear.I doubt I would have broke a chromoly drive shaft.My pinioun angle was checked the day before found to be right were its supposed to be.

chicane

Its not a pinion angle issue... and never was.

It you have any interferance with the TA and the shaft or floor pan... a chromo shaft wouldnt have the same failure mode... but at least you would have a witness mark that would say >> look here <<.

I would inspect the chassis and TA for anything that could induce such a failure... like an exposed brake cable hanger, seat belt anchor or anything that is part of the TA itself.

The shaft didnt brake from power application. I bet it was from something hitting the shaft. And that something may be part of your car...

BeemerZ28

iTrader: (5)

chicane

thats exactly what I was going to respond with earlier it sounds like the intergrity of the CF shaft was comprimised. ie. scratching the shaft, causing freying, and and extreme loss in capacity of the shaft hence the break-up.

+1 for checking the underside of the car for anything the could have touched the shaft and scratched it. Remember to look through the whole suspension travel path of the shaft because that 5k dump prolly means you are compressing your rear suspension pretty good.

Jimmy P

iTrader: (177)

That sounds very reasonable and might be the cause. I stayed away from carbon fiber, because it is supposed to stay clear of anything that may touch it. I was afraid that it may touch something like the y-pipe and cause a failure.
My aluminum driveshaft is rated to 1200 hp, and holding up fine in my car so far. (780 torque!)
I am surprised that they replaced the driveshaft after a year, and surprised that you chose to reinstall the new one in your car. I would of just sold it, buy an aluminum, then use the left over cash for more mods.

mullenh

iTrader: (1)

I hope you found your answer. My thought is the same shaft in an automatic would be fine because you preload the shaft when you foot brake it, With a clutch dumping at 5000 rpm and 600 hp the 'shearing' force would be terrific and the shaft just can not handle it. good luck