They are all question you should ask the guy rebuild the axles (temper, heat treat, tolerance, factory specs) as an experienced machinist myself with a strong interest in metallurgy I can tell you this, if they are set up to do these, heat treat processes are used, weld is done be a competent welder with the correct processes/filler, the is no reason they can not be rebuilt back to or better than factory specs. If you are concerned, call the shop that's doing the rebuilds and ask for references of people that have used their rebuilds, any shop worth doing working with will be happy to give you the names a satisfied customers are at least give your name to said customers to call you back. Also ask how many failures they had any/or who long they expect their product to last. I realize they are out to sell their product, but they are going to be able to help you with your concerns, weather justified or not, better then people that may have no experience with any type of axle much less a rebuild one in a combine... or may have experience with a poorly (home done bird crap weld job) executed rebuild... or could even by 1 out of 1000 that have failed, or maybe after talking to the company you'll decide that the rebuild isn't worth it as you'll be doing it again next year with damage to the housing as well... Just be sure the company is 100% transparent and isn't trying to hide anything that pertains to the rebuild (except processes specifics that if relieved may lose them a job to someone else)
