Bolt Grade for Fan Assembly

Having been an engineer for the past 30+ years I do know how various grades of materials fail and grade 3 fasteners will stretch a huge amount and neck down 30% or more before they break and the few lug nuts I have snapped over the years have had little or no visible necking before they break which is indicative of a high strength steel fastener. Also, the typical recommended torque for a 1/2" grade 3 bolt is 55 ft-lbs and a grade 8 is 90 ft-lbs, with recommended wheel lug torques in the 75 ft-lb range the fasteners have to be much stronger than grade 3 or you will be yielding them every time you torque them. The ones I have snapped only happened after putting a pipe on a breaker bar. I can snap a 1/2" grade 3 with a wrench without any extra leverage.

So, I don't believe for a second that a wheel lug is a grade 3.

FWIW, I am not in favor of poly bushings on one of our old mopars because they are not sealed and will wear out much faster than stock rubber bushings. This is because the poly bushing slides on the shells and with nothing preventing road grim from getting in between they will grind away vs the bonded to the shells rubber bushing which twists for its motion.