What's that sound??? Cracked Flywheel???

[Hobbz]

Background:
305 TBI 120k miles on the odo, I believe it is original to truck
Does not have the recirc valve in the exhaust
Sounds lower in engine
Goes away after 5 or so minutes of running

I am planning on a new engine next winter but was planning on driving the summer on this one after all the body work was done... No huge deal if it is terminal for the engine, but...

Video of it running just after startup.

http://www.youtube.com/watch?v=uOolNCJ8DM0

I am thinking bearing or flywheel cracked. What do you all think?

 

[MrMarty51]

Usually a rattle that goes away after the engine is warmed up would be a piston slapping in the bore, this does sound like flex plate is cracked, it is an automatic transmission, right ??
Check the fan and pulleys for tight too.

 

[Hobbz]

Yeah, I said flywheel, mean flex plate. It is a 700r4 transmission. My buddy said it sounded like loose torque converter bolts. I youtubed it, and it sounds exactly like the others. I am going to pull the inspection cover this weekend and check them and see if I can see the flexplate.

 

[J Knight]

Yeah, I said flywheel, mean flex plate. It is a 700r4 transmission. My buddy said it sounded like loose torque converter bolts. I youtubed it, and it sounds exactly like the others. I am going to pull the inspection cover this weekend and check them and see if I can see the flexplate.

This is exactly what it sounds like to me.

 

[77 K20]

Also look at the starter when you have that inspection cover off. I had a starter "fall apart" near the gear and I think it was a thrust washer that would wander out and then get banged around by the flex plate. Made about the same noise. And then eventually the washer would get knocked aside and it would be quiet for awhile.

 

[Hobbz]

Thanks everyone. I will update after I get a chance to work on it.

 

[HotRodPC]

I'm having a similar problem with my 454 and I'm about to determine its a broken flywheel. Do update us and let us know what you find out.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

 

[87ChevyR10]

Since we are on the subject of flywheels and torq converters, my truck makes a jingley sound as soon as the starter lets go and the engine fires up. Doesn't make the noise any other time. Truck turns over easily. Nothing negative has resulted from it. Any idea what I could be hearing?

Thx!

 

[MrMarty51]

Since we are on the subject of flywheels and torq converters, my truck makes a jingley sound as soon as the starter lets go and the engine fires up. Doesn't make the noise any other time. Truck turns over easily. Nothing negative has resulted from it. Any idea what I could be hearing?

Thx!

Could be the starter solenoids slug is gummed up a bit and not immediately releasing when the ignition key is let off of.

 

[Hobbz]

Flexplate to TQ converter bolts are fine... Thats is the good news.

Flexplate to crank bolts are loose or flexplate is broke around those bolts. I can turn the TQ/flexplate back and forth about 1" without the crank moving...

Next question, without counting the current one, do I have a 168 or 153 tooth flywheel, or does it matter???

 

[HotRodPC]

Flexplate to TQ converter bolts are fine... Thats is the good news.

Flexplate to crank bolts are loose or flexplate is broke around those bolts. I can turn the TQ/flexplate back and forth about 1" without the crank moving...

Next question, without counting the current one, do I have a 168 or 153 tooth flywheel, or does it matter???

Where it's going to matter, is which starter you use. Whether you use the one with staggered mounting bolts, or bolts straight across from each other. So in relation to which starter you have it does matter for certain.

 

[Hobbz]

Thanks. I am going to pull the trans as soon as I done with my rockers and cab corners. Local parts store carries both in Stock along with a new rear main seal so that will get changed too

 

[89Suburban]

Good job tracking down the problem

 

[Hobbz]

Finally got a video to show everyone. If you look close near the end, you can see the crack
http://www.youtube.com/watch?v=skjt8cXvYIE

 

[HotRodPC]

That video will pretty much confirm for me, that's what's up with my 454 C20 too. I was pretty sure it was. I needed it anyway, it has about 5 teeth that are chewed up and every now and then, the starter lands there and misses engagement. Thanks for posting.