OK, here is my tale of woe, hopeully someone else will learn from my
trials.
Last summer, the engine of my SC Riv 3.8 with 140k miles started making
a terrible noise from the general area of the timing gear. So off came
the belt tensioning assembly, water pump, and harmonic balancer. Whoa!
One DISINTEGRATED harmonic balancer! The rubber that held the two
pieces together had shredded and there was about 30 degrees of play
between the timing tabs and the hub. I replaced it with a DORMAN
(made-in-China) balancer for about $100. Replaced the timing chain,
gear, and water pump, as long as I was there. Not a difficult job, just
a bit annoying because of the stuff you have to move to get to the bare
front cover.
Car ran great, for exactly 405 miles.
Limped home one night around Thanksgiving and as I creeped up the
driveway, it started spewing oil out the front seal all over the place.
Three months of miserable cold weather and the Riv had to sit on the
driveway until three weeks ago when I put together enough will to see
what happened.
The answer was pretty quick in coming. When I took off the balancer
(remember, made in China for $100) it came out in two chunks. Seems
that the hub had fractured at the keyway and this was the cause, I
figured, for the "running like crap". The splintered hub must've taken
the front seal with it, causing the oil hemorrage. Off came the front
cover (in order to replace the front seal) and just for the hell of it
I took a real good look at the oil pump, which on the 3800 is driven by
the crank, just behind where the balancer sits. Good thing I did. The
housing was cracked from the balancer failure and this is where I was
losing oil.
I took the balancer back to Lee Auto in Arlington Heights IL and told
them my tale. They took the old balancer and gave me a new one, with no
questions. Just for the hell of it, I took the new balancer to my
machine shop of choice and this is the purpose for my rant.

The NEW BALANCER WAS DEFECTIVE!!!!!!!!!

Seems my machine shop guy Joe teaches at a local jr college and
mentioned that the Dorman guy told him these things are failing left
and right. So we checked the new one very closely. Not only was the
keyway cut too wide, it was cut too shallow on one end; torquing this
one on the crankshaft was sure to fracture the hub. Most likely this is
what happened to my first replacement balancer - it started to fail as
soon as I installed it.

One might be quick to label all stuff from China as crap and I'm not
sure I would argue that. Certainly I will never go the cheap route on a
mission-critical part again.

Perhaps the better lesson is to very carefully inspect (maybe a better
word would be MEASURE) mission-critical parts.