Strange rattle sound from rear of engine or tranny

[texaslawman]

Hello all, and thanks for such a helpful site. My problem is this. Recently, my wife's van started making a rattling noise either when idling or when slowing to a stop. If this makes sense, the rattle sounds rotational as if something is loose and being tossed around inside an open metal cavity. Yesterday, I changed the oil and used Slick50 engine treatment, and I also changed the tranny filter and fluid. The engine itself sounds better than it has in years, and the tranny shifts smoother as well. The van has about 142000 miles. I can't locate the rattle to narrow down any suggestions, but, when listening closely to the engine, I can't hear the noise if I focus on the front (near the pulleys). If I focus my attention on the rear of the engine (near the tranny), the noise seems to be coming from the bell housing area, but again, I can't pin point it to say for sure. Let me stress that the engine and tranny are operating near perfectly. Any ideas or suggestions? Thanks for you time.

[texaslawman]

Sorry to all. This may be of use. The engine is the V6, 3.8L and the tranny is the AXOD Metric.

[Blue Bowtie]

Way too many possibilities. Any way you can post/link a sound clip?

There is the torque converter, flexplate, trans pump, main drive chain, the splined hub for the sprockets, all of which would be major repair. There is also an inner CV joint right at the transmission chain cover, which could be a problem on accel/decel.

Does the noise occur only when the vehicle is moving, or while sitting still? In gear only, or even in neutral? Coasting in neutral?

[wiswind]

If you have ramps, drive the front up onto the ramps.
Place in PARK, turn engine OFF, and block the rear wheels to prevent vehicle movement.
Slide in under the front end, and look where the transmission is near the engine oil pan. On mine, there is a thin metal shield that goes up in between the transmission and engine. Mine was loose, making some rattling noise.
I tightened the small screws that hold it in place.

[texaslawman]

Well guys, I found the problem. $140 and I'm back in business. I hadn't crawled far enough under the vehicle. I traced it to the catalytic converter. It was damaged and had a large chuck rattling inside. I had it replaced at a local muffler shop, and the problem is gone. Thanks for all your time and help! This is a great site, I'll be back

[road_rascal]

$140 for a converter? Brand new? That's a bargain!

[texaslawman]

Yes, it was brand new! I was pretty pleased with the price myself when other muffler shops wanted $425+ saying they would have to replace the entire catalytic system. This was a weld-in job with a new unit, and my baby's baby is purring like new.

[wiswind]

The "Y" pipe replacement from Walker is just over $300, add about $100 for labor.....is still better than the list price of $1200 for the "Y" pipe from FORD.
I did the replacement, and it is worth every penny of the $100 labor charge.