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flywheel failure....


ST#97

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For all you guys running stock flywheels, here is reason enough to spend the money and get an SFI rated flywheel and a steel bellhousing if you can.

 

This is...was, a stock Ford flywheel from a 2000 Mustang GT. It only had 21k street miles and about 3k track miles on it. This turns out to have been my driveline vibration I couldn't seem to track down and also trashed the main bearings in the motor as well as two balancers and the timing chains and the pressure plate was cracked in 6 places and sheared all the dowel pins. The clutch disk however was perfect so I now have a spare. What's amazing is that I was still winning races with this thing.....just SO happy it never failed while running but this explains why I started missing shifts which is a rarity for me. The center fell out with just a light hit from a hammer and the FW was wobbling nearly 3/8".

 

http://www.aggie97.com/flywheel%201.jpg

 

http://www.aggie97.com/flywheel%202.jpg

 

http://www.aggie97.com/hole.jpg

 

 

Also, http://www.ddperformance.com is selling aluminum/Fidanza FW's pretty darn cheap.

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www dot ddperformance dot com is the correct address.

 

I have a 00 GT, havent had that issue but Ill be sure to closely inspect the flywheel tomorrow when the engine comes out. No worries if I find anything like pictured above. I've got a fidanza aluminum flywheel at the engine shop with the rest of the rotating assembly.

The Fidanza alum. flywheels just took a price jump they had been around $319, now places like Summit and Jegs think theyre worth $379. I just checked D&D performance theyre still listed at $329 on their website.

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It has been my experience over the years that the reason flywheels and flex plate break that way is because it was not bolted in "clean" or "square" to the crankshaft or because it lost a balance weight. Since the clutch cover bolts to the flywheel thus becoming part of the flywheel, it too can be the cause if it is not flat or out of balance. Since clutch/flywheel are typically dusty/dirty all to often clutches and flywheels are taken for granted when it comes to cleanliness during the installation process. One small piece of dirt or a burr between the flywheel and the crank is all it takes.

 

Guys like Don Garlits can tell you how important scatter shields are as a result.

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Was there any evidence of a metallurgical defect that started this or is it simply excellent grip + good torque = stronger that the stock material?

 

After some more research, this appears to be a common failure among 8 bolt GT cranks and NOT the 8 bolt cobra cranks. Different materials from what I understand.

 

As for what caused the failure, tough to tell. The car did see some drag strip duty on slicks pulling 1.5 60's at full weight for about 80-100 passes before I realized the turn at the end of the strip was more fun!!!

 

And thanks for correcting the web link. I entered it at work in a hurry and the box that showed up is a fidanza piece. I also got the replacement friction material for it now just in case I ever need it at the track.

 

Marshall, the car is still in pieces and the motor is in Michigan expecting it to return mid march...be afraid because if you think I had freight train torque before....there's even more coming and the car will be much closer to weight than the 130-160lbs over last year!

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I am curious... I have always used "puck" style clutches in my Mazda race engines and they are awesome. I simply can not think of any better clutch to run in a race car since they are virtually indestructible. Believe it or not I have used the exact same clutch thru 4 seasons of racing including running the entire Timex Endurance series, the Pro Sedan series, teaching students, AND winning the 25 Hours of Thunderhill all in the same season.

 

But recently while researching what to use in my GT350 I have been reading that puck style clutches are hard on flywheels and cause them to crack in high performance applications. When I look around the websites who sell mustang clutches I tend to see non puck style clutches. So my question is... what type of clutch are most of you guys running in small block Fords and are you having other flywheel issues?

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But recently while researching what to use in my GT350 I have been reading that puck style clutches are hard on flywheels and cause them to crack in high performance applications. When I look around the websites who sell mustang clutches I tend to see non puck style clutches. So my question is... what type of clutch are most of you guys running in small block Fords and are you having other flywheel issues?

 

This was a dual friction kevlar puck style clutch from D&D. I ordered a new clutch identical to before and it is a continuous surface instead of pucks... Wonder if they figured something out.

 

Oh, and that clutch has been in their since early on when I roasted the stocker on slicks drag racing and it is still in great shape with half the life left in it!

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Interesting! I found an article today that said not to use a puck clutch on the street due to cracking flywheels and then it went on to say using puck clutches in racing applications is ok simply because racers tend to inspect the flywheel more routinely than in street usage. The fact that the puck does not wear out is the cause of more heat which wears out the flywheel the same as in cracked brake rotors scenario.

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Interesting! I found an article today that said not to use a puck clutch on the street due to cracking flywheels and then it went on to say using puck clutches in racing applications is ok simply because racers tend to inspect the flywheel more routinely than in street usage. The fact that the puck does not wear out is the cause of more heat which wears out the flywheel the same as in cracked brake rotors scenario.

 

Yes, I should have inspected it more frequently however I am afraid many of us try to do as little teardown as possible between events. I am going to modify my post event inspection sequence for sure!

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Interesting! I found an article today that said not to use a puck clutch on the street due to cracking flywheels and then it went on to say using puck clutches in racing applications is ok simply because racers tend to inspect the flywheel more routinely than in street usage. The fact that the puck does not wear out is the cause of more heat which wears out the flywheel the same as in cracked brake rotors scenario.

 

Unless you are looking for a weight savings, the standard duty (AutoZone or O'Reileys) clutch should work fine. I have a $140 AutoZone clutch in my AI car and it works just fine with 3 years on it so far. YMMV

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Interesting! I found an article today that said not to use a puck clutch on the street due to cracking flywheels and then it went on to say using puck clutches in racing applications is ok simply because racers tend to inspect the flywheel more routinely than in street usage. The fact that the puck does not wear out is the cause of more heat which wears out the flywheel the same as in cracked brake rotors scenario.

 

Unless you are looking for a weight savings, the standard duty (AutoZone or O'Reileys) clutch should work fine. I have a $140 AutoZone clutch in my AI car and it works just fine with 3 years on it so far. YMMV

 

Rather than simply start tearing a car apart to inspect it, my crew chief mentality would start asking myself, "How many others have had this problem and if so with what type of flywheel and clutch? Is there any truth to the fact that puck clutches cause them to break? How much advantage is there in an aluminum flywheel vs a cast iron one and so on."

 

Regarding my Mazda's which can run 9000 rpm all day long thanks to an awesome engine builder, I have never had any flywheel issues and always used a puck clutch that was bullet proof. Of course there is nowhere's the amount of horsepower from in my Shelby's so I really want to find out what front runners who race hard use. More importantly I want to know what the front runners that (key words) DON'T BREAK are using. I gotta tell you, I am amazed to learn the stock clutch holds up that long!!! That's simply amazing. Do you ever drop the clutch?

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