Jim,
The original rods were just longer 300SDL rods & with the EXTRA load that just didn't work well. MOST rod failures that I've seem are from "LIQUID" compression. Some fluid in the cylinder, ie: bad injector OR head gasket leak.
THE new rods are thicker & beefed-up in every way possible. THAT is why MB says only replace is a complete set, because they are that much heavier. Close to 1 oZ.

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