Rattling Sound coming from Bell Housing

[absolvd]

I've got a 1998 Eddie Bauer with about 180,000 miles (4.0L SOHC V6). The other day I started hearing a rattling sound coming from underneath the engine. The best way I can describe it is it sounds like loose bolt rattling around inside the engine. I checked the tensioners on the front of the engine and it doesn't seem to be coming from there. I put on a stethoscope and it sounds to me like it's coming from the bell housing. I pulled off the starter and inspected the outer portion of the flywheel, which appears normal. I'm thinking that it could be the inner portion of the flywheel where the bolts are or the torque converter. It shifts fine other than going into reverse kind of hard, which it has done the last 50,000 miles. Any thoughts?

 

[drdavis_ks]

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.

 

[absolvd]

Thanks for the reply. It sounds like you're thinking along the same lines as I am. I also got no codes of any kind when I scanned it. I'll check to see if it makes the noise still at higher RPMs.

 

[absolvd]

The noise definitely gets much more faint above 1000 RPMs. I listened at the back of the head with the stehoscope and couldn't hear much, so I'm more convinced that it is the flex plate and not the rear timing chain. That said, if I can replace the rear timing chain while I have the tranny out, I'll do it ($68.00). Anyone know if it can be done with without pulling the engine?

 

[absolvd]

OK. I pulled the tranny and was somewhat surprised to find the flexplate in perfect condition. When I listened with a stethoscope, the noise was certainly coming from the bell housing. I'm sending the torque converter out tommorow to be tested, which I think and hope is the problem.

 

[absolvd]

I got the torque converter back from being tested and everything is fine. Now I'm real confused. If anyone has any insight, please let me know. I'm wondering now if it's not something in the tranny (pump or something).

 

[justanother1]

I just had the flexplate in my wife's break around outside of the bolts.

Check the spacer between the flexplate and the crank. I've read this is a common problem.

 

[daan-o]

what is the flexplate failure caused from? lead foot? I have a similar knocking but i think mine is a torque converter because if you push the throttle in too hard it makes a super loud squeeling noise like forks rubbing on a ceramic plate and it losses power going to the wheels. I also have the 2-3 shift flare and its been like that for almost 2000 miles i just baby her...people hate it.