Where can i get data about load ranges in auto parts?

Question

I need to know the load/stress values on auto parts such as shafts, axles, fasteners, etc.

Answer 1

Fasteners simple the're numbered. Other parts are more difficult. Heat treatment case hardning and materials. ASTM standards for metal is one place. Manufactures keep there processes secret because almost everything is copyrighted and patented.

Answer 2

Fasteners usually have tensile codes stamped on the heads of the cap screws. The marks are identified by a series of lines from the outside of the hex towards the center.
No markings = grade 2 cap-screw.
3 radial lines = " 5 "
8 " " = " 8 ''

Exact break (failure) tests come from individual fastener companies.

Failure ratings of shafts, axles, torsion bars would need to come from the individual maker of the product. For instance an aftermarket axle or half-shaft may have separate failure values. If you knew someone who was a metallurgist who had access to hardness testers and SEM instrumentation exact metal "recipes" could be identified. Then you'd know exactly which metal grade you had. There are hundreds of mixtures which include iron, nickel, chromium plus trace elements which make-up formulations.
Theres a vast difference between cold and hot rolled steel. Shafting metals are formulated to be formed machined and heat tempered.