Can't find the noise, please help!

[Bushwick]

(car in sig) OK, had a weird "zinging" sound and thought it was the heat shields, but while out with car today noise came back. Had all new valve stems put in and while car was on lift, asked them to inspect. Shop guy couldn't find anything. I looked as well, and everything is tight. The heat shield between the exhaust and drive shaft does have a tab broken up front, but banging it didn't produce the same sound. I also checked the drive shaft in case it was touching, but no wear marks.

 

If I didn't know any better, I'd say something was loose and (barely) touching the flex plate teeth making a ziiinnng sound. Starter is tight as well. I'm stumped. Definitely from the back of engine, near or under firewall area.

 

Does a 4EAT even have a flex plate inspection cover?

 

Anything inside the bell housing cavity known to break or come loose, possibly falling or laying on the flex plate or able to come in contact with teeth? 

[Rooster2]

My vote, is............... it is still the heat shields on the exhaust system. Banging on the exhaust system, or the heat shield won't necessarily produce the shrill zinging sound that you are attempting to hear. In my experience, the sound is tied to the engine rpm, which will vibrate the exhaust system at certain rpm's. My fix has been to find a good size bolt to hammer in as a wedge between the shield and exhaust system to stop the shield vibration and noise. If the shield is broken at multiple tabs, or rusted badly and floppy, then I tear the shield off to stop the noise. I don't park in high weeds with a hot exhaust system, so heat shields to prevent grass fires are not a concern to me. Suggest trying either of these fixes, before doing anything else. Also............... Some guys have also attached a large screw down hose clamp around the shield to prevent the shield from vibrating.

[nipper]

Cheap fix on the shileds, use large cheap hose clamps on the shields. It also makes for easy and cheap way to rule out things.

[Fairtax4me]

The teeth are on the torque converter, which should not be touching anything. But you can remove the starter to check the starter housing and look in through the starter hole at the TC to see the teeth.

 

It is possible the lower bellhousing cover is loose and is rattling or bent and touching the TC.

[Bushwick]

Heat shields are all tight. One of them already had a large worm clamp wrapped around to prevent movement. Only the long shield that runs under the drive shaft had 1 tab broken. I'll wedge something between it to 100% rule out, but it'd have to be vibrating at a super high speed and making contact with an object which it's not. Sound it too pronounced and the pitch is higher and consistent sounding.

 

@Fairtax, can you explain the lower bellhousing cover to me? It's aluminum, right? What can bend? The valve covers leaked on this area for awhile and some residual grime is caked on the bottom of the engine and bell housing. To me it looks like a 1 piece unit?

 

Anyone with a 4EAT trans bellhousing pic detached from engine, preferably with whatever little parts still attached and a pic of the back side of the engine block? The sound is definitely getting transmitted through STEEL, and NOT aluminum, meaning it sounds like a steel object touching the teeth the starter turns. 

 

Is it possible something on the starter is loose (internally, relating to the cog gear) and either vibrating or sliding slightly and touching the surface while moving? Car turns over fine w/o any starter issues. If I have to resort to a video, I will.

[Bushwick]

^^ Anyone?

 

Going out now to fix a couple things, then putting some more time into finding out what's causing the noise. Any pics of a pulled trans bellhousing would be helpful. Did you read my last post Fairtax? Will be helpful going into it, especially if pulling the starter yields no resolve. Just concerned if something IS touching the teeth, then definitely need to get it out before something get's launched through the housing or worse.

[Fairtax4me]

The covers is at the bottom of the bellhousing. It's bolted to the engine block and and extends downward then back until it meets the transmission case. Its very hard to see or get to with the engine in the car.

[Bushwick]

Thanks. After doing some other things with it, I started up briefly and for the first time it made some of the sound at idle. Quickly looked under car and found/felt a shield (that appeared/was tight) that despite being secure was making noise (runs length of pipe ahead of rear cat). Quickly worm clamped it. Then, while shutting the driver rear door, I heard another brief rattle. Thought WTF, they were all tight enough when under car, and 2 different mechanics looking it (plus me) over found no issue. So now the center shield between the drive shaft and body was acting up. Wedged a section of 3/4" heater hose between the body and shield. Started up and drove a bit. STILL getting a sound but it's not as much of flex plate teeth "zing" anymore and sounds more like another section of shield. Really weird. Almost wondering if the colder temp was affecting the metal or something.

 

Anyways, appreciate the feedback everyone.