It's hard to say for sure without hearing it in person, but the 4.3 vortec is known for making balance shaft noise. My '97 does it a little. My brother's '99 makes a lot of noise. To me it sounds like main bearing noise. It's really never changed much over time on either of our vans and doesn't seem to be an issue in any way.
GM had a kit to fix the noise, but I believe it's been discontinued. I know one guy who disabled the balance shaft to stop his noise. The engine ran a little rougher at low rpm, but the noise stopped.
Here's a link
http://www.s-10crewcab.com/og1/modinfo/ ... eshaft.htm
GM had a kit to fix the noise, but I believe it's been discontinued. I know one guy who disabled the balance shaft to stop his noise. The engine ran a little rougher at low rpm, but the noise stopped.
Here's a link
http://www.s-10crewcab.com/og1/modinfo/ ... eshaft.htm