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what does a cracked flex plate sound like?

josh9mile

NAXJA Forum User
Location
spokane
Just did an aw4 conversion on my wheeler. Gets a sound similar to a fan blade hitting something but not quite as fast. Only happens under a load, and idling in park or neutral when the jeep is on an incline. Does not do it when cruising, but give it just a hair more throttle and it does. I didn't notice any obvious cracks in the flexplate when I installed it, but I'll admit I didn't look very hard because I figured they would be fairly prominent. Any thoughts?
 
You can pull the inspection plate and turn the engine over by hand. The cracked flexplates I've seen have always cracked at the bolts for the torque convertor.
 
The cracked flex plates I've heard have all sounded like rod knocks at idle. Using a mechanic's stethescope usually helped me pinpoint the noise to the bellhousing.
 
There are also two other possibilities. One is a loose torque converter, which can also be confirmed by removing the inspection plate. Or it might be the catalytic converter, in which material breaks loose inside and causes a rattle.

I have a similar rattle, mostly at idle, that I think is the cat. (Everything else looked OK upon inspection.)
 
Bought a new flex plate today and got it installed. Still makes the same noise. ���� Waste of a day and $100
 
Just did an aw4 conversion on my wheeler. Gets a sound similar to a fan blade hitting something but not quite as fast. Only happens under a load, and idling in park or neutral when the jeep is on an incline. Does not do it when cruising, but give it just a hair more throttle and it does. I didn't notice any obvious cracks in the flexplate when I installed it, but I'll admit I didn't look very hard because I figured they would be fairly prominent. Any thoughts?


I've heard something about a worn exhaust hanger at the TC cross member can cause a banging noise. Sorry no personal experience with it though. Since you were working in the area it might be worth a look.
 
Thanks for all the input guys. It's fixed! It turned out to be a worn out starter. The gear wouldn't suck all the way back in after starting, it would freely slide in and out whenever I tilted the starter. Which would explain the noise when going up hills or accelerating. Would be just enough to have the gear just barely touch the teeth on the flex plate. Sometimes it's the stupidest fricken things!
 
Thanks for all the input guys. It's fixed! It turned out to be a worn out starter. The gear wouldn't suck all the way back in after starting, it would freely slide in and out whenever I tilted the starter. Which would explain the noise when going up hills or accelerating. Would be just enough to have the gear just barely touch the teeth on the flex plate. Sometimes it's the stupidest fricken things!

Wow!! That's a new one.
 
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