Re: Attempt to join Audi tranny to ford bellhousin
Don't want to rain on anyone's parade, especially looking at all the effort that's been spent. It's my fault for not catching this thread earlier.
Welding trans cases is probably a viable option provided it's done properly. But here's what you have to consider.
Welding aluminum and retaining the original strength is a very tricky proposition. The welder is only concerned with one thing, the integrity of the weld, like appearance and lack of occlusions etc., he's not concerned or even necessarily knowledgeable about the comparative strength of the piece.
What you need to know.
A. the alloy of each piece and whether or not it's heat treated.
B. the alloy of the weld filler rod and it's strength.
After further research I don't think heat treatment of the assembly after welding is an option because warpage exceeds the tolerances of the bearing bores in the cases and typical filler rods do not respond to heat treatment.
If the pieces are originally heat treated you may not loose that much strength depending on what level it's heat treated to.
A continuous welded seam all the way around a bellhousing case seems to me like a link in a chain. That case is only going to be as strong as that weld, which can be researched starting with the filler rod alloy specs.
Furthermore it's possible, depending on the alloys of the bellhousing and transaxle that the area adjacent to the weld is even weaker than the filler rod, depending on the alloy and whether it was heat treat hardened.
Some things I've learned since first posting to this thread.
typical casting alloys and their mechanical properties, the F stands for unhardened condition
Chart at bottom of page
http://www.alumalloy.com/specs.html
Cases should be jigged to a solid holding fixture for weld pre-heat and welding. More specific info is in "Performance Welding" by Richard Finch.
and here's what my welder friend had to say.
start quote
the casting alloys typically used are
354, 355, 356, 357
Best bet is to clean both pieces completely, including a soak in some
strong solvents to remove any grease imbedded in the surface.
Jig them up, preheat both pieces up to about 500 degF, and TIG weld
using 4047 filler rod.
When the welds are done wrap in wool blankets or bury in Vermiculite or
powdered lime to keep in the heat and allow them to cool very slowly.
Vermiculite can be bought very cheap at garden supply stores.
Dump a bunch in a steel 55 gal barrel, drop in your piece and dump in
enough vermiculite to cover the part.
Dig it out the next day.
end quote
This could all be academic if your primary consideration is cost. Because the price of a Ford clutch/flywheel compared to say a Porsche setup is considerable. And if you look at your setup and decide that even if the case breaks it won't be a safety issue because the transaxle will remain captive and not lock up the rear wheels then more power to you. Been there done that.