Flexplate removal
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
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From: Reno NV
Flexplate removal
Hey everyone, my newest project is a 76 Corvette with a 350 (I think) and an automatic. It's making a rattling/clanking noise when it runs, and I believe it is the flexplate rattling around. The noise is not always there (just most of the time), and it increases with RPMs, but again, it's not consistent.
I'm a pretty novice mechanic, but I'm going to try to tackle this one. I've pulled the inspection cover, and there is no obvious damage. I was told to unbolt the flexplate from the torque converter to see if it is firmly attached to the crank (if it wiggles at all, it's probably cracked?).
First of all, am I on the right track?
Second, how do I rotate the torque converter to reach all of the bolts? I found that I can spin it by hand (not easily) with a wrench on one of the bolts, but I'm not sure if this is bad for the engine. Is there a specific direction to turn?
Thanks for all your help guys; I'm sure I'll be back with more questions.
I'm a pretty novice mechanic, but I'm going to try to tackle this one. I've pulled the inspection cover, and there is no obvious damage. I was told to unbolt the flexplate from the torque converter to see if it is firmly attached to the crank (if it wiggles at all, it's probably cracked?).
First of all, am I on the right track?
Second, how do I rotate the torque converter to reach all of the bolts? I found that I can spin it by hand (not easily) with a wrench on one of the bolts, but I'm not sure if this is bad for the engine. Is there a specific direction to turn?
Thanks for all your help guys; I'm sure I'll be back with more questions.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Since you'll not be turning it a lot, it doesn't matter which direction. That is a good place to start looking for the noise. An easy way to turn the engine is to put a 15/16 socket and rachet on the alternator pulley nut and turn it clockwise. Use your hand to put pressure on the belt at the under side of the pulley so it will grip better.
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
Likes: 0
From: Reno NV
Since you'll not be turning it a lot, it doesn't matter which direction. That is a good place to start looking for the noise. An easy way to turn the engine is to put a 15/16 socket and rachet on the alternator pulley nut and turn it clockwise. Use your hand to put pressure on the belt at the under side of the pulley so it will grip better.
Where do I go from here? Drop the transmission and see if the noise still persists (eliminating or confirming that it is a transmission/engine problem)? Bolt the flex plate back to the torque converter and look underneath while the engine is running?
Thanks guys.
Racer
Joined: Feb 2008
Posts: 497
Likes: 0
From: Streator Illinois
Hey everyone, my newest project is a 76 Corvette with a 350 (I think) and an automatic. It's making a rattling/clanking noise when it runs, and I believe it is the flexplate rattling around. The noise is not always there (just most of the time), and it increases with RPMs, but again, it's not consistent.
Thanks for all your help guys; I'm sure I'll be back with more questions.
Thanks for all your help guys; I'm sure I'll be back with more questions.
If not, sound waves are transmitted through frame and engine/drivetrain materials and may not always originate from where they seem to be heard. Are you sure the noise is not coming from the front of the engine? The noise you describe could also be a water pump, harmonic balancer, or an AC clutch and/ or compressor.
I suggest using a long screwdriver or length of tubing as a stethoscope to better isolate the source of the noise.
Terry
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
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From: Reno NV
A group of enthusiasts suggested it could be the flex plate. It was thought originally to be a rod knock, but it doesn't really have the characteristics of a knock (goes away sometimes, coming from the middle of the car). You're right, I don't know that it's coming from the flex plate, but that was my best guess, and where I was lead by others. Upon closer inspection, though, it seems to be fine.
I guess I will bolt it back up and run the engine with the car in the air to see if I can get a better guess.
EDIT: Last time I listened to it, it definitely wasn't coming from the front, but I will fire it up again and see. Also, the noise was definitely a metal on metal 'clanging' noise, which got louder with RPMs, but isn't always there. Apparently it has worsened with time, but the engine hasn't thrown a rod yet.
I guess I will bolt it back up and run the engine with the car in the air to see if I can get a better guess.
EDIT: Last time I listened to it, it definitely wasn't coming from the front, but I will fire it up again and see. Also, the noise was definitely a metal on metal 'clanging' noise, which got louder with RPMs, but isn't always there. Apparently it has worsened with time, but the engine hasn't thrown a rod yet.
Last edited by Shoobie; Aug 21, 2008 at 09:17 PM.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Since you have the flex-plate unbolted you could run the engine and see if you still have the noise.
I would drain the oil into a clean drain pan and look for bearing material or remove the oil filter and dump it out and look closely a the oil for metalic coloring. You could also cut apart the oil filter and inspect the paper for metal.
I would drain the oil into a clean drain pan and look for bearing material or remove the oil filter and dump it out and look closely a the oil for metalic coloring. You could also cut apart the oil filter and inspect the paper for metal.
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Although difficult to isolate, that is what you must do. Try different operations to duplicate the noise.
Car stationary.
Running car forward.
Running car in reverse.
If vehicle is in motion when noise is apparent concentrate on the driveline.
Idle car and with stethoscope listen at various locations.
Metal to metal clunking will normally be accompanied by wear marks visible under lighted conditions. Score marks should be obvious. An exhaust manifold or header gasket leaks sound like metal/metal. A bent flexplate access cover will create a ticking noise if bent in far enough, but again would be apparent by wear marks where the contact is taking place.
Patience and a good ear will yield results!
Car stationary.
Running car forward.
Running car in reverse.
If vehicle is in motion when noise is apparent concentrate on the driveline.
Idle car and with stethoscope listen at various locations.
Metal to metal clunking will normally be accompanied by wear marks visible under lighted conditions. Score marks should be obvious. An exhaust manifold or header gasket leaks sound like metal/metal. A bent flexplate access cover will create a ticking noise if bent in far enough, but again would be apparent by wear marks where the contact is taking place.
Patience and a good ear will yield results!
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
Likes: 0
From: Reno NV
Since you have the flex-plate unbolted you could run the engine and see if you still have the noise.
I would drain the oil into a clean drain pan and look for bearing material or remove the oil filter and dump it out and look closely a the oil for metalic coloring. You could also cut apart the oil filter and inspect the paper for metal.
I would drain the oil into a clean drain pan and look for bearing material or remove the oil filter and dump it out and look closely a the oil for metalic coloring. You could also cut apart the oil filter and inspect the paper for metal.
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Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
Likes: 0
From: Reno NV
Although difficult to isolate, that is what you must do. Try different operations to duplicate the noise.
Car stationary.
Running car forward.
Running car in reverse.
If vehicle is in motion when noise is apparent concentrate on the driveline.
Idle car and with stethoscope listen at various locations.
Metal to metal clunking will normally be accompanied by wear marks visible under lighted conditions. Score marks should be obvious. An exhaust manifold or header gasket leaks sound like metal/metal. A bent flexplate access cover will create a ticking noise if bent in far enough, but again would be apparent by wear marks where the contact is taking place.
Patience and a good ear will yield results!
Car stationary.
Running car forward.
Running car in reverse.
If vehicle is in motion when noise is apparent concentrate on the driveline.
Idle car and with stethoscope listen at various locations.
Metal to metal clunking will normally be accompanied by wear marks visible under lighted conditions. Score marks should be obvious. An exhaust manifold or header gasket leaks sound like metal/metal. A bent flexplate access cover will create a ticking noise if bent in far enough, but again would be apparent by wear marks where the contact is taking place.
Patience and a good ear will yield results!
Burning Brakes
Joined: Feb 2004
Posts: 758
Likes: 14
From: Ville de la Baie Quebec. A winner is just a loser who tried again.
Noise comming from the flex plate will normally not be herd when under load or normal driving, it will be appairante on start ups and idling. Use a stethescope to help diagnose. Also if the bolts from the plate to the converter are ok make sure to check the ones holding the plate to the crank,,, (as me how I know) you can shave down an open end wrench (the box side) and tighten them up..... hope this helps.
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
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From: Reno NV
Originally Posted by Michel B
Noise comming from the flex plate will normally not be herd when under load or normal driving, it will be appairante on start ups and idling.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
You haven't indicated if you have the noise when the car is sitting still or just when it's moving.
Thread Starter
Intermediate
Joined: Jan 2006
Posts: 29
Likes: 0
From: Reno NV
Just make sure the torque converter is pushed back from the flex-plate and I wouldn't run it more that a minute or so. The center of the t/c will still be riding in the rear of the crankshaft, but should not hurt anything for a short run. If you still have the noise with the flexplate bolts out, then you will know it's in the engine somewhere.
You haven't indicated if you have the noise when the car is sitting still or just when it's moving.
You haven't indicated if you have the noise when the car is sitting still or just when it's moving.
