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Old 10-23-2005, 06:24 PM
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Flywheel cracked

One of my project cars is an 89 IROC-Z. My trnasmission was rebuilt a few years back and then began leaking again. I learned to just deal with it since the 700R-4 was really difficult to take out of the car. I finally got the ambition to take it back out and I noticed that the flexplate is cracked on it. The cracks are around the bolts that bolt it to the engine. How does this happen? I have a gut feeling that this might also be why my tranny front pump seal went bad cause I thought that there was some play in the torque convertor from it. The car is not that souped up, and I see no reason for this to happen other than that I am pretty sure it had nitrous through it before I bought it because of some tubes welded to my TPI intake that are now plugged.

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Old 10-23-2005, 09:22 PM
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A tranny guy told me later Chevys with the smaller flywheel bolt pattern & one-piece rear seal are prone to breaking like that if someone besides Grandma drives them. He recommended an American-made aftermarket flex-plate that's a little beefier than stock.
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Old 10-24-2005, 08:47 PM
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I guess I should update my flywheel vs NOS that I was thinkng about. I really don't plan on driving this car like granny.
Chris Diedrick
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Old 10-24-2005, 09:17 PM
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cracked flywheel

You should also look at a couple of other things to make sure this doesn't happen again. Make sure that your bell housing looks OK and your dowel pins are in place and in good shape. If you engine and trans aren't lined up something has to give! Look at your torque converter, the knob on the engine side of it is there to align the crankshaft and the center of the torque converter and pump. Make sure the torque converter bolts and mounting lugs (where it attaches to the flywheel) look good. Check the fit of the torque converter in the pump, if there is a lot of play the bushing and front seal should be replaced. I would consider replacing the seal anyways since you have the trans out. Also, did you locate the leak so you can fix when the trans is out?

When you reinstall the trans make sure you mate the engine and trans together without using the bell housing bolts to pull them together. Make sure the torque converter is back far enough into the pump and then make sure it can still spin when the engine and trans are bolted up. Then slide the torque converter ahead and get all three bolts installed before you tighten them up the last turn or so. All of this will ensure that the trans, torque converter, and flywheel (also called flex plate) are all lined up. This should prevent the flywheel from cracking again, unless you go a little crazy with the nitrous!

Good Luck,
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Old 10-28-2005, 08:36 PM
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flywheel crack

I have been a GM tech for quite a while and I can assure you its a GM thing. In dealerships I've worked at I've replaced and seen replaced literally hundreds of cracked flywheels. Camaros were notorious for it,they usually make a rattling sound to let you know they're fixin to die.
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