I know it sounds like a kind of vague topic so let me elaborate. It doesn't sound like it is coming from the engine internally but more so from the flywheel area, possibly torque convertor. I pulled off the flywheel inspection cover and everything seemed to check out OK. The torque convertor bolts were tight also. The sound almost sounds like a rod knock but seems to be provoked at low RPMs : between 600 - 1500 rpm. As the engine revs up, the sound tapers off and is not audible. The sound is not coming from the exhaust. The engine runs and drives perfect. Anyone have any ideas or experiences that may provide some insight on my problem? Thanks

 

Sounds like a cracked flex plate.

 

Yeap! that's what I would think it was too. Common problem actually.

 

It could just be an exaust leak. Probably a small small some where around a weld. Or just collector leak.

 

Flexplate

 

I'll third the cracked flexplate. Seen lpenty even on bone stock TBI cars... where they got the power to crack them is beyond me.

 

Thanks for the response. I'll check it out tonight.

 

i have a friend here in TN who has a 91 GTA who recently had that exact same problem... ended up he had something come loose inside his TC...

 

I had that problem and was terrified of it being a spun bearing. i was all prepared to call the machine shop to find out how much to redo a block and grind it for a stroker crank, when i got the "bad" news from myfather who was working on the car in a different place (had it towed home from where I live in the summer and he took a look) and he found a cracked flexplate. It was all solid, but was loaded with hair line cracks. A new flexplate solved that problem. Its cool to tell people that my motor made so much power it broke the flexplate. It happened on my first g-tech run too which was kinda funny. I also drove the car with the flexplate messed up for like 150 miles as it held oil pressure just fine. Yeah Im not too bright.

 

Yeah it's cool to say that, but it would be a little bit of a lie, it has nothing to do with it... at the TV station I used to work at, the News Dept. threw away a perfectly good Chrysler K-car with about 80k miles or so on it because it knocked, and their "mechanic said it needed a new engine"... an employee bought it for like $150, changed the FP, had a pefectly good (well, within the limits of a K-car, anyway) car that he drove for another 6 or 7 years that I know of..... I can guarantee that car didn't break it because of excessive power

 

The elongated bolt holes and not thinking ahead are probably what broke it now that i think of it.