- Thread starter powernut
- Start date
Vast majority of ally castings are silicon rich alloys with little if any mag. There's more magnesium castings (90 odd % mag alloys) appearing on cars but they're very different to aluminium magnsium alloys which only contain a few % mag. Aluminium-silicon-copper is a popular flavour due to it's combination of strength and machinability 'as cast'. Weldability varies, most are weldable but they're prone to solidification cracking with some being quite tricky. Others contain quite a lot of zinc and can be a right mare to (more rarely) virtually impossible. What's the gearbox out of? I've welded quite a few (VAG, Ford, Borg Warner, Getrag etc).
Filler wire for cast ally will be one of the silicon flavours, best choice will depend on exact alloy which is unlikely to be known (in which case 4043 is best bet) but worth checking out all of the casting marks on the case as some manufacurers helpfully cast the actual alloy designation into the part- a lot of the VAG boxes being AlSi9Cu3 for example although newer Passats (and their floorpan sharing cousins) use an AZ91 mag casting and the cost of the filler wire will bankrupt you
Tungsten flavour doesn't really come into it, go with usual preferred choice for AC welding. Box will need preheating (min of 80-100C, max of 200), cooling rate not so critical as cast iron and depending what it is you plan on doing may well need machining afterwoods- doesn't take much misalignment to end up with a box that eats bearings (or worse) when cutting and shutting bellhousings or the like
Filler wire for cast ally will be one of the silicon flavours, best choice will depend on exact alloy which is unlikely to be known (in which case 4043 is best bet) but worth checking out all of the casting marks on the case as some manufacurers helpfully cast the actual alloy designation into the part- a lot of the VAG boxes being AlSi9Cu3 for example although newer Passats (and their floorpan sharing cousins) use an AZ91 mag casting and the cost of the filler wire will bankrupt you
Tungsten flavour doesn't really come into it, go with usual preferred choice for AC welding. Box will need preheating (min of 80-100C, max of 200), cooling rate not so critical as cast iron and depending what it is you plan on doing may well need machining afterwoods- doesn't take much misalignment to end up with a box that eats bearings (or worse) when cutting and shutting bellhousings or the like
well i have to u know ur stuff pal , every reply is always really helpfull , i tigged a vw gearbox from a vag passat , basicly from cold , as it soon heats very quickly and used white tungsten and 2.4 alloy filler rods i noticed when it comes were the gearbox alloy melts it goes a redy colour ,but tig weld fine , but tryed a starter moter and gave up as it just kept bubbleing up then exploding lol , i think ill kept away from old vw gearboxs as magnezium , really goes up in flames/smoke so bloody fast
, i lost my eye browes thew one , 
