Cracked flex plate? Loud hammering sound
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Cracked flex plate? Loud hammering sound
Hey guys, I need another opinion or 10. My camaro has developed a horrible hammering sound. Metal on metal.
i recently put longtube headers on that didn’t fit the best. But no noises. Slowly at startup I heard a hammering sound start. Thought it was headers settling in. Kept getting worse until the point I stopped driving the car. Drive fine and couldn’t hear the noise driving but at startup and shutdown could hear it bad. Kept getting worse.
had my wife bump it a few times today and I swear it’s coming from torque converter area. I’ll upload a video in a bit but thought someone that has had a flex plate crack could chime in. Doesn’t look cracked but I know that doesn’t mean much.
really just looking for some confidence this is the noise before I go and pull a trans.
video coming.
thanks guys
i recently put longtube headers on that didn’t fit the best. But no noises. Slowly at startup I heard a hammering sound start. Thought it was headers settling in. Kept getting worse until the point I stopped driving the car. Drive fine and couldn’t hear the noise driving but at startup and shutdown could hear it bad. Kept getting worse.
had my wife bump it a few times today and I swear it’s coming from torque converter area. I’ll upload a video in a bit but thought someone that has had a flex plate crack could chime in. Doesn’t look cracked but I know that doesn’t mean much.
really just looking for some confidence this is the noise before I go and pull a trans.
video coming.
thanks guys
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
What do you think? It’s just a stock flex plate. Maybe it’s met it’s end of days
Joined: Sep 2005
Posts: 28,030
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Cracked flex plate? Loud hammering sound
Flex plate usually crack right around the crank flange. Can't see that part of it.
Doesn't sound like a motor problem. It's not continuous.
Unbolt the converter and push it back into the trans, start it up, and see what happens.
It's SOOOOOOPPPPPPEER EEEEEEEEEEEZZZZZZZZZZZY to change the flex plate without pulling the trans, if it comes to that. Can be done in prob less than a half-hour.
Doesn't sound like a motor problem. It's not continuous.
Unbolt the converter and push it back into the trans, start it up, and see what happens.
It's SOOOOOOPPPPPPEER EEEEEEEEEEEZZZZZZZZZZZY to change the flex plate without pulling the trans, if it comes to that. Can be done in prob less than a half-hour.
Joined: Nov 2008
Posts: 2,108
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From: Milwaukee
Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: Cracked flex plate? Loud hammering sound
Did you hand crank it around and look for rust or crack evidence? The one place it stopped looks like theres no torque converter bolt....are they there and tight?
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
ok. All bolts are in it. No visible cracks. Flexplate just had a few extra holes.
looks like a storm coming. I’ll unbolt the converter and slide it back and see what I can see and hear.
thanks
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
And sofa I never knew you could get enough room to pull one with trans bolted. That’s a huge relief.
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Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
Sofa I seen you posted this once before
You DON'T have to take the transmission all the way out.
Drain the fluid, remove the drive shaft, unhook the shifter cable and cooler lines, and take out the fill tube. Support the trans, remove the crossmember, and take off the torque arm bracket. Take off the converter shield, and remove the converter bolts. Take out all the bell housing bolts except the 2 bottom ones; then put 2 about 6" long bolts in the upper BH bolt hole on each side; then remove the bottom 2 bolts. Slide the trans back as far as it will go.
That will give you room to get a long box-end wrench up in there and remove the flex plate bolts.
Drain the fluid, remove the drive shaft, unhook the shifter cable and cooler lines, and take out the fill tube. Support the trans, remove the crossmember, and take off the torque arm bracket. Take off the converter shield, and remove the converter bolts. Take out all the bell housing bolts except the 2 bottom ones; then put 2 about 6" long bolts in the upper BH bolt hole on each side; then remove the bottom 2 bolts. Slide the trans back as far as it will go.
That will give you room to get a long box-end wrench up in there and remove the flex plate bolts.
Thread Starter
Joined: Dec 2004
Posts: 2,042
Likes: 18
From: Lincolnton, NC
Car: 88 IROC
Engine: 97 5.7 Vortec LT4 hotcam
Transmission: 700 r4
Axle/Gears: 3.73
Re: Cracked flex plate? Loud hammering sound
Done some more research on it. Pretty sure it’s the flexplate. Driveway isn’t the flattest and it’s hot so going to haul it to my dads shop and fix it there. Grabbed a sfi flexplate from a local race shop inventory reduction auction fairly cheap. I’ll let ya know what I find in a couple weeks.
Junior Member
Joined: May 2022
Posts: 95
Likes: 14
From: Long Island
Car: 88 IROC-Z
Engine: 350 H.O. w/ 113 heads (SUM-8800)
Transmission: 700r4 stage 2 500hp
Axle/Gears: 2.73 Posi Yawn Fest
Re: Cracked flex plate? Loud hammering sound
I recently did a swap to a 350 H.O. crate motor in my car and used a bad torque wrench to attach the flywheel bolts and they ended up backing out and making that same exact noise, at one point it got so bad that I could move the flywheel back and forth on the keyway, I'll post a video.
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