Coilover failed...help

Not a metallurgist, but you're right, I am a Commercial Transport Technician. The failure analysis I've learned was mostly during training courses for Eaton transmissions (10, 13, 15, and 18spd) and differentials, which is my specialty in the trade, but I have read through some material from Caterpillar on the same subject, since I find it facinating. That said, I don't claim to be an expert on the subject, I only have a fairly basic understanding of it.

The case here with the coil spring is very much like what your customer wants you to find when they have a broken gear tooth in their transmission that is under warranty. If you have an "inclusion" in the metal, and beach marks out from it, it is considered a manufacturing defect, and parts and labour are covered. If the whole fracture is rough and granular, then it us considered a "shock load" failure, and not warrantable. It isn't terribly difficult to shock load a drivetrain when you have 1850 - 2050 ft-lbs of flywheel torque and grossing out at 140,000lbs with a set of trains. (Can I tow that with my Tundra??) A spinning wheel suddenly grabbing traction is one easy way.