Is My Flywheel Cracked?

98form · April 18, 2009

Hello All. Thanks in advance for any help.

I have used the search function and have not found that much about flywheel problems. I recently picked up a 2001 Suburban with 120K. I am trying to diagnose a noise coming from the back of the engine/front of the transmission area. It is most noticable when I start it up. It is fairly quiet for about 5 seconds and then I hear something that sounds almost like a chain dragging/something loose that soon settles down into a tapping sound. Every now and then I will hear the chain dragging sound and it does accelerate with the RPMs. After the truck warms up, it is more of just a tapping sound, but always coming from the rear of the engine/underneath the truck near the tranny.

I don't think that it is Piston Slap. It doesn't sound like it anyway. I did a lot of reading on that to make sure. I have a 99 NBS Sierra with the 5.3 and it will occaisonally give a little piston slap at startup when it is cold or when I haven't started it in a few days. This truck has 175K on it and runs great. No chain dragging sounds.

I don't think it is a heat shield either since it accelerates with the engine. Could it be something in the Transfer Case? I have read that there is a chain in there.

If it is a cracked flywheel, what causes this? If you have any experience with flywheel problems, please share your story.

Any other suggestions?

Thanks again.

Jay

Original_Prankster · April 18, 2009

Drop your inspection cover, clean it out, reinstall and make sure the bolts are tight

VMax2007 · April 18, 2009

Sounds like maybe your starter is not disengaging completely.

98form · April 18, 2009

Ok, so where is this inspection plate located? What does it look like/how big is it?

I don't think it is the starter because I have had that happen to me before on another car and that seemed to be a more constant grinding sound than what I am hearing from the Suburban.

Thanks for the suggestions!

Jay

bubba33 · April 18, 2009

It covers the front of the tranny a few bolts hold it on. I had one crack on a 77 blazer with a 350. It was making noise so I unbolted the flywheel for the torque converter and the noise stoped.

Original_Prankster · April 18, 2009

It looks like this,

bossier62guy · April 18, 2009

It covers the front of the tranny a few bolts hold it on. I had one crack on a 77 blazer with a 350. It was making noise so I unbolted the flywheel for the torque converter and the noise stoped.

FYI....flexplates are used w/ automatic transmissions, flywheels w/ manual transmissions.

bubba33 · April 18, 2009

It covers the front of the tranny a few bolts hold it on. I had one crack on a 77 blazer with a 350. It was making noise so I unbolted the flywheel for the torque converter and the noise stoped.

FYI....flexplates are used w/ automatic transmissions, flywheels w/ manual transmissions.

I started to say flexplate but he said flywheel and I know the differance. thanks

98form · April 18, 2009

Is there any fluid that I need to catch when I remove the inspection plate? If I do need to replace the flexplate, does that involve dropping the trans? How much would I be looking at to replace it?

sonjaab · April 18, 2009

No fluid !!!!!!!!

Yes the trans. will have to come out.

Wingnut · April 19, 2009

The torque converter bolts coming loose can make a helluva racket sort of like what you're describing. And you can tighten them by removing the starter and having some nifty tools.

98 Z71 SLT · April 19, 2009

Do this.

Remove inspection cover

Remove 3 15mm bolts that attach flexplate to torque converter.

Take a long screwdriver / prybar, and shove the converter BACK towards the trans.

This allows the engine to be ran seperate from the transmission

Start the engine and listen for noises.

If you STILL have the same noises, you have a crankshaft / lower end problem in the engine.

Report back and let us know...this whole procedure only takes 15 minutes...

98form · April 19, 2009

I went outside, jacked up the Suburban and looked for this inspection plate. I don't really see anything like that other than what looks like the bellhousing that is part of the transmission. Is this what I am supposed to remove? It doesn't look like I can take that off without dropping the transmission.

I did see a small, maybe 2" around, cover that I could pop off with a screwdriver. I did this and it gave me access to the flexplate. I turned the flexplate by prying with a screwdriver in between the teeth. All of the teeth look fine and I can't see any cracks in the flexplate. I did not remove the starter and check for loose bolts because I wanted to check with you guys again about that inspection cover. Please advise.

98 Z71 SLT · April 19, 2009

Dude...yeah you are right on it...

Take the 2-inch cover off, remove all the flexplate bolts, fire it up and report back to us...

EDIT...might be easier to take the 2 starter bolts out, shove the starter out of the way, then remove flexplate bolts, just quickly install starter to fire it up

98form · April 20, 2009

I removed the two starter bolts and shoved the starter out of the way as much as I could. I removed a plastic cover that was around the starter. This gave me a little more room to get to the flexplate. I see what looks to be 3 bolts holding the flexplate to the torque converter. These bolts have a large hex head, not something that a 15mm wrench will fit. I don't think I have anything large enough to remove these bolts. Are these the ones I need to remove? They look to be tight, nothing loose there. There are definitely no cracks in the flexplate. It looks good.

Super Stealth,

Thanks for the help. I have a few questions for you. Would the torque converter make the kind of noises I am describing? Now that I have seen that the flexplate is in good shape and the bolts appear to be tight, what am I going to gain by removing the bolts? If I do have a problem in the lower part of the engine or crankshaft, what could it be? Bad bearings? I just changed the oil and did not see any metal shavings or pieces on the drain plug.