I have a knocking noise from the under carriage Saturn 2001 L200. We have
checked the exhaust system, changed the front sway bar, changed both
front struts, and the driver side ball joint and tie rod end.The noise occurs
while driving straight ahead at slow speeds and on bumpy roads.Any help
would be appreciated.

Examine and replace the transmission shock mount(s) that have failed, or possibly the engine motor mount (top and or bottom) that has gone bad ...

I have a 2000 LS1 Saturn with a similar or maybe the same problem.
I was told by the Saturn dealer that the engine cradle mounts needed to be replaced. Estimate $400.00 [img]smileys/smiley11.gif[/img]
The mounts are located in each corner of the engine cradle.

Good Luck