I can't remember the year that GM changed the 2.5
engine from cam gears to chain drive...but in the 80's,
most of the 2.5's still had the cam/crank gears. The
cam gear is a fibre gear and would wear out. As the
teeth wear, the engine starts to sound like a diesel
engine. The fix is to replace the gears. You can
drive it like that without damaging the engine, but
eventually, the teeth just shear off and the engine
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