cracked flexplate sound but not cracked ?

[blazer2007]

I have a stock 350/350 rebuilt about 10,000 miles ,driven in a small town of 60,000 people, no freeways or anything here. Had a rattle noise for bit in the fall of 2019 ,couldn,t find anything then a rattle again in the spring of 2020 for maybe 10 seconds, then in the fall it did it again but didn,t go away. I checked everything with a piece of hose and no noise in the valvecovers ,oil pan etc. Definitely coming from torque converter area. Flex plate has no wobble. Tried a new starter and no luck, no visible marks on any thing. Good oil pressure, makes the noise in all gears, never goes away. Noise goes with the RPM,s. Still noise with T.converter loosened and slid back. Slid tranny back and checked all bolts. I can,t see any cracks and flexplate tings nice when you tap it with a wrench. Am I chasing my tail or will the flexplate make this terrible noise with no cracks, I don,t see how but weird things happen. I found a u-tube video of a similar sound mine makes. Driving me crazy as I can,t find the cause. Sorry for the long thread . https://www.youtube.com/watch?v=DPk7CGEOqwk

[Tom]

If you pull the convertor off and slide it back and it still makes the noise its not the flexplate or trans making the noise. Look elsewhere.

[AussieinNC]

Does it make the noise if you leave the flywheel stamped steel cover off?

[blazer2007]

Originally Posted by AussieinNC

Does it make the noise if you leave the flywheel stamped steel cover off?

No, no cover on

[ChevyRacefan]

Flex plate bolts are loose. Would be my guess.
But how do you know it has no cracks? Doesn't sound like you removed the transmission.
Did a weight spot weld, let go, and weight is causing it.

[blazer2007]

Originally Posted by ChevyRacefan

Flex plate bolts are loose. Would be my guess.
But how do you know it has no cracks? Doesn't sound like you removed the transmission.
Did a weight spot weld, let go, and weight is causing it.

I slid the tranny back about 5 inchs and checked the bolts and could have a good look at the flex plate. I also turned the flexplate and had a good look at all the welds. I guess I will remove the flexplate and try a new one. I just couldn,t see any evidence for the noise. I,ve never had this happen in all my 40 yrs. and was thinking I,m missing something so I thought I would use all the combined thinking from this forum. I have all winter but the truck is in a carport and is cold.

[Ironangel]

Might check your starter clearance...Sometimes they'll move around even if the bolts are tight. Might add a starter brace while your down there...Good luck PS. Your response to removing the converter shield was unclear. Does it make the noise with the shield removed? If so, then check the starter. If not, then hammer out the contact area on the cover or replace it with a plastic one. Hitting coons, possums, dogs or rocks can bend those covers and cause that sound...Get a video with your phone laying under the truck before and while the truck is starting and running (with the cover off)...

[blazer2007]

I didn,t ever get around to putting a cover on , so no noise with cover off. Did put a new starter on just incase the starter was hitting but still made the noise and I could get a good look at the starter while it was running to see if anything was hitting. No video as the tranny is pulled back from the engine .

[Dead Parrot]

I chased an intermittent noise for a while in my 75. Sounds like something rattling on something else either in the area of the firewall or back of the motor. Turns out that pressing down on the passenger side of the transmission hump where it turns vertical will make it quit. Still don't know for sure what is making the noise. Could be some part of the rusty floorboard rattling from engine vibrations.

Noises can come from a lot of places.

[blazer2007]

Floors are replaced. I know what you mean about sound. If the front end noise is coming from the right side it ends up being the left. I,ve learned not to assume. Thanks anyway. Made some progress, removed harmonic balancer as had abit of a wobble,didn,t look bad but wanted to put a new one on anyway , I guess they cant transfer noise, Loosened 3 flexplate bolts but time for supper and get warm. At least I,m doing something instead of thinking about doing something.

[kwmech]

Originally Posted by blazer2007

I didn't ever get around to putting a cover on , so no noise with cover off.............

So with the cover removed there is no noise?

[cadillac_al]

to me, a clacking cracked flex plate sounds a lot like a rapping rod knock. Is this an intermittent noise or is it constant now?

[blazer2007]

Originally Posted by kwmech

So with the cover removed there is no noise?

sorry noise all the time, brain and typing didn,t co-inside

[blazer2007]

Originally Posted by cadillac_al

to me, a clacking cracked flex plate sounds a lot like a rapping rod knock. Is this an intermittent noise or is it constant now?

It is constant, all rpms and all gears . the rpms are nice and smooth thou.

[paul mora]

Not 100% sure but didn’t someone have a similar problem recently and it was the distributor causing the noise.

[cadillac_al]

Originally Posted by paul mora

Not 100% sure but didn’t someone have a similar problem recently and it was the distributor causing the noise.

or an oil pump?

[blazer2007]

I did listen to the oil pan when running and it didn,t sound like it was coming from there but who knows how sound travels. It is a loud noise if you listen to the video I posted

[ChevyRacefan]

Check the back side (engine side) to make sure the bolts are not long and smacking the block somewhere,
Might want to check crank thrust play. If the transmission converter was pushing to hard , or whatever. and wiped the thrust bearing. the crank walking could cause it.

[blazer2007]

took the flexplate to the tranny shop and he said nothing wrong with it. He said put it back together and listen some more and he bet me a coffee saying he thinks is a header gasket. He said they can make a bad noise sometimes like I described. Will check crank end play first thou.

[Captainfab]

The noise in your video is NOT an exhaust leak. It is a metallic sound.

[Getter-Done]

I have had noises that were hard to track before.

I used a Stethoscope like the one in the link below to get close to the problem.

Yes I am sure some will say use a broom stick.
This fits in the ears better thou

Link: https://www.harborfreight.com/mechan...787f869da899c4









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[cadillac_al]

Originally Posted by Captainfab

The noise in your video is NOT an exhaust leak. It is a metallic sound.

That's not is actual video. Maybe an actual video would help us. The flexplate has been ruled out. The engine was run with torque converter slid back so that is ruled out too. Hopefully it is a header leak. A rod knock would be a little deeper fuller sounding than that video in the first post.

[blazer2007]

I have good oil pressure and a rod knock would change as the temp got hotter [so I,m told] and again it sounds outside, pass. corner by starter.

I did tell the tranny guy it sounded metallic he still said give it try and I will, nothing to loose but alot of swearing if it is. I,ll put it back together and see, weather permitting . We always get a cold blast in Feb.

[blazer2007]

One thing I did remember, I did turn the engine over with no coil and no noise if that means anything.


Another is the header collectors don,t have gaskets, they have that ball type pipe made by headman and are about 8 yrs. old, maybe !

[Getter-Done]

You could take the plug wires off one at a time

This would let you know if it was a certain cylinder.

I suggest using this type of pliers in link below.

Link: https://www.walmart.com/ip/Alltrade-...reight&veh=sem









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