grade 5 vs grade 8 bolts(chassis/suspen)

[crazy longhorn]

This post is a spin from another post that was about stainless fasteners. I am working with plain steel fasteners, so I figured to start a new post would be better than "hyjacking" a post per say. I have heard it said by several guys that grade 8 is not good on chassis , or suspension parts.....I am no engineer, but if you crawl under your truck, & check the markings on the factory bolts holding the front crossmember.....you will find they are grade 8! The eye bolts on the springs (factory leaf truck), also have grade 8 bolts! The bolts holding the steering box are grade 8, as well as the idler arm(factory). there has been a lot of discussion on 5 vs 8 on the fasteners.....i tend to go a bit overkill on some things, but have always felt that a grade 8 was the way to fly on suspension pcs. the U bolts will be a softer grade, I guess so that they can "wrap" the axle properly? the last Bell tech spring hanger kit I installed (90 GMC shortbed), had grade 8 fasteners, to mount the hanger to the frame I have followed this with every pc that has been removed/ replaced on my chassis. I run 7/16 grade 8 hardware, with pinchlock nuts on my spring hangers, trans crossmember, & carrrier crossmember.....both crossmembers are custom pcs.I feel that the fit on the bolt in the hole is important.....no slop, they were drilled to fit tight enough that a few had to be tapped in with a hammer. I have yet to have a grade 8 bolt come loose, or break, on the bottom side of the truck. crazyL