Please explain your grade 5 bolts that failed and where they were used and their size. Not just a blow-off story. They don't fail on any of our uses on our trucks.
Obviously a rusted bolt or over torqued by user or fastened part failure is not what we are talking about. We are talking about the strength of the bolt to carry the load.
As for people who say grade 8 is necessary and disregard others. They are not able to do strength analysis, just be antagonists trolling posts. Wannabe engineers. Telling you to ignore members. Not a good look but very typical behavior..... over and over. Nasty wording.
You can use any grade you want, anywhere. The strength, in shear, of four Gr 5 3/8 bolts is about 18,000 lbs.
