Technical Welding on rear end

I am welding on ladder bar mounts and shock mounts, I know many people that have warped-bowed the housing, resulting in wheel bearings going out

any tips tricks to use?

 

advice on welding brackets to rear end housing here is one, dozens of threads on the subject, the search function s your friend

 

Dustyrustee's advice in the link above is spot on.
You could probably skip the pre-heat though if your weld runs the full circumference of the tube - if your brackets are not designed this way, then add the heat on the opposite side either with a torch (how much heat?), or maybe better by running a bead all the way around with the same amperage, then grinding this off after. Done it this way a few times with no effect on the tube's straightness - I break the circumference into eight segments and run a second weld opposite the previous one (ie 12 then 6 o'clock; 3 then 9 etc)
Work fast so cooling (and shrinking) is minimised....