Not exactly a G-Body question, but...

[Uncletruck]

One trick I use to determine if its bearings is to drain a little bit of oil and replace it with a bottle of STP oil treatment. If the noise lessens noticeably or goes away, it is likely to be worn bearings. If there is no difference, it's probably something else. Torque converters like to develop rattles as they get older, often mistaken for engine bearing noise.
-UT-

 

[dan2286]

I use to be a ford tech at a dealer here you can't give me a mod motor they have the most problems egr messing up plugs blowing out of the head blow by crown vic and mustang there plastic intakes leak and gaskets never stay the coils on them are pricey and a mother to put on and only last 100k.The gm 3800 is ok if its not the one with a blower but the auto transmission be hide them is iffy.The 98 up 3.8 ford is ok 03 up mod motors are getting better but not prefect.Theres not many engines i love ford would be the 300 inline 6 the 429/460 and the Windsor small blocks.Gm the v8s are ok the 4.3 is ok the iron duke you can kill 3800 good but like i said gm put a crappy transmission to most.

I have a Grand Prix with the 3800. Yes the transmission is junk. I first had it rebuilt at around 100k for a blown diff. 50k later it broke again from the pump shaft twisting and snapping. I have to admit that me beating the sh*t out of the car didnt help it at all!! The hd transmission in the supercharged version only has an upgraded differential, all other internals are the same. There is a company that has these cars running 9 seconds with there modified transmission, so there is parts available to strengthen all of the weak points.