Need some experienced opinions.

[taylorpro]

Hey guys. I drive a 99' Explorer XLT with the 4.0 SOHC engine. I'm having a rattle around the bellhousing area that I've read more and more about and it seems to be fairly common. I've already removed all the heat shields around the two cats under the tranny, and the converters SEEM tight. you can smack em with your hand, rubber mallet, anything, and can't get any sound out of them. The sound is barely noticeable at idle in park unless you're listening for it. Typically I hear it in drive when leaving a light. It will make the noise coming from a stop up into first gear power band and go away for the most part after it gets up in rpm. Now, the engine DOES have 170k on it, and I don't know the history of the timing chains and guides. BUT from what I've read, this doesn't seem to fit the same symptom. The noise isn't louder at start up, even after it sat for a week while I was on vacation. Oil pressure is strong at all times. I've read some threads with people having issues with the flywheel's breaking around the flange of the crank. And also some of newer Ex's having rattle in the actual torque converter. But mine shifts smoothly, especially for the mileage, and it just doesn't seem right to me that there could be a problem in the TC. But what do I know? Anyway I'm curious to think what guys think would be most probable. IF its most likely the fly wheel, I'll save up some coin and go ahead and pull the engine, replace it, the TC guide, and go ahead and do the guides and chains while its out. BUT if you all think it's not that issue, I'm all ears to other idea's. Thanks all

 

[drdoom]

Mine was the idler pulley, sounds strange but for fifteen bucks and five minutes labor, I'm not complaining.

 

[taylorpro]

Its deffinitely not the front of the engine. Well, not this noise anyway. It sounds EXACTLY like a rattling heat shield. Very metallic. Noisy, but not violent.

 

[deweyville65]

Sounds to me, without hearing it, cracked flexplate. I had this same thing on a Chevy truck years ago.

 

[taylorpro]

Sounds to me, without hearing it, cracked flexplate. I had this same thing on a Chevy truck years ago.

I'm thinking the same thing. Especially because post #2 in this thread describes EXACTLY my symptoms. And, since I've addressed the exhaust, short of the TC, I can't think of any other reasonable thing.

http://www.explorerforum.com/forums/showthread.php?t=240042

here is what I found with same rattle:
Rattle/Knock was flexplate, not timing chain
My 99, 4.0 SOHC, Auto, 145,000mi, Sport had a rattle/knock. I read plenty on timing chain death and was preparing for a massive overhaul. Upon total failure, found it was the flexplate. I removed the starter and found I could turn the flywheel (flexplate) with my finger.
The symptoms were a metallic rattle (like a heat shield or something) but only under 1000rpm. Over 1000 rpm it was smooth and quiet...normal.
It was very subtle, more annoying than loud. I'm pretty good but I could not isolate the rattle beyond engine-passenger side. Even changed spark plug wires figuring knock...they needed changing anyway.
Other than that, it ran and drove normal, no CEL or codes thrown. Never overheated or delivered unusual gas mileage. Failure was without warning. Tried to start up from a stop light...motor rev'd up but old green wouldn't move, kind of buzzing and sawing sound, expensive sounding. A daily driver, it went about 3 weeks from 'first noticed' to 'won't move'.
Flex plate is $100-ish, book says 5.5 hours to R&R transmission.
SO...rattle/knock does not always indicate a timing chain/tensioner issue.