Axle Shaft Material

I recently had my axle shaft machined and now it needs to be heat treated but I am not 100% sure on the material. I had a post about this earlier but I can't seem to locate it. I was told and a few others seem to believe that the axle shaft is made from 4140 chromemolly but does anyone know what GM makes their FWD axles from? Or have any idea so its close enough so I can get it hardened.

When it comes to this stuff I have no idea what I am doing.

Thanks

alot of computer recycling companies have a spectraometer (sp?) and it shoots a ray on the metal and tells you the chemical make up. may want to call around to see if anyone has one. they are very PRICEY!