the_merv

iTrader: (88)

What's this goin to sound like guys..I am having a weird sound and the way it's happening doesn't add up to what we have checked out..

NovaCain383

iTrader: (8)

I had one break one time. Sounded like something wrong in the transmission or something wrong in the bottom end. Depending on where it is broke or cracked will depend on how it sounds. Mine sounded like a main bearing knocking in the bottom end. Couldn't tell it was broke without unbolting the torque converter. You can tap it with a hammer and it will have a rattle to it instead of a ring or bell like sound. What is the sound you are getting?

SBP

Gilbert@Ace Racing

A broken flexplate can sound typically is repetative, like a main or a rod knock. Nova Cain is right on the money, unbolt the converter from the flexplate and tap it.. it should ring out. Also, you can visually inspect it... to a certain extent when the converter is unbolted.

g

NovaCain383

iTrader: (8)

Also if you do find it to be broke or cracked. Don't waste your time buying a stock one to replace it. Spend the money for one that is SFI approved. Even though it is a little more, it is worth it in the long run.

SBP

the_merv

iTrader: (88)

This is what I got...I just went through a Lifter change, so the Top-end is still good, Rockers are good, etc..

Car at cold idle has 65psi, Car idles fine, no noise at all.

Car warms up..starts a real sparratic knocking in the low-end, not as loud as a Rod Bearing, but loud enough, and it trips out the Knock Sensors.
I checked the Cylinder Walls when I had the Heads off, nothing wrong there..no Piston slapping the Head, and when I pull the Wire to each Cylinder, the noise doesn't change.

It only does it when it warms up, and it's really sparattic, and Oil Pressure is really responsive, starts at 65psi and goes up no problems when you give it Throttle..

It's got me mind boggled..

Gilbert@Ace Racing

Why were the lifters replaced?

g

the_merv

iTrader: (88)

Yup..and there is no problems at all with the Valvetrain..no broken Springs, anything..

It only makes this noise when it warms up...

Gilbert@Ace Racing

Huh?

Why were the lifters replaced?

g

the_merv

iTrader: (88)

I had a lifter Collapse..sorry, missed the why part..

I replaced them with LS7 Lifters, and there is no problems with anything in that area at all, just this rattling noise when it warms up..

LS1MCSS

iTrader: (18)

I had a flexplate crack once. It sounded like a rod knock while the car was at idle. I could hold the brakes and bring the rpm up a little and there would be enough pressure on the flexplate to stop the knocking noise. Try that with your car.

Gilbert@Ace Racing

Good Talking to ya "Merv"! keep me in the loop... between myself and the boys next door at Xtreme H/P I am sure we can help you get to the bottom of it!

Good luck dude!

g

the_merv

iTrader: (88)

Well now at cold Idle it knocks like a mother focker..75psi Oil Pressure..and that was starting it this morning. I'm dropping the K-member and looking at everything.

1_badt/a

iTrader: (8)

i just had mine do the same thing, and dropped the tranny, ended up being the flexplate. had a big crack, just lift it up and go under and have a friend start it 4 u so u can see if it comes from in between the tranny and the engine. just my .02 cents. hope u fined the problem.

Gilbert@Ace Racing

Ruh ro.

g

junior28570

iTrader: (22)

+1

Had the same thing. Putting pressure on the drivetrain would twist the flex plate enough so the knock would go away. Just putting it in gear and doing a little brake toque would clear the noise right up. Knocked steady when it was in neutral. Of course reving the motor would only encrease the frequency of the knock. My flex plate was cracked from each mounting hole all the way up to the starter gear.

Spellbound

Another broken flex plate expierience here...
Sounded like a rod knock...
One Day I went to start it up and the starter froze, the engine would not turn over. So I pulled the starter and low and behold the crack/break was right there for me to see, lol...

On a car club cruise one time, a member reved his car in a tunnel and broke his..made the same exact sound as mine. He only got one more start out of it before his locked up and had to be towed.

Gilbert@Ace Racing

Yep, I would bet a dollar to a donut that there are countless broken flexplate stories out there! Especially with all of the engine mods that go down!

g

sixvi6-camaro

iTrader: (9)

My broken flexplate only made an occasional clank noise at idle.. where I really noticed it though was when I was starting the car. It would make a couple loud clank sounds as soon as the starter would engage and usually one or two more just as it started.

the_merv

iTrader: (88)

Alrite..to add more detail..I had said knock, but it's more like a tick..a really fuggin loud tick, sometimes consistant, sometimes not. It's between #4 and #6 Cylinders in the bottom end. Cancelling out Cylinders does nothing to the noise, and the Oil Pressure stays the same.

Now to add the new info..
I tore it completely down to the Engine today. Flexplate is flawless...

The Engine is at the House, Sunday morning I'm tearing apart the bottom-end, take a little look at things...

junior28570

iTrader: (22)

If we've learned nothing else from this thread ... a broken flex plate can and will sound like something has gone wrong in the motor