Welding Trans Cases

How would you service the clutch assembly even if welding was possible?

by removing the transaxle from the engine, just as you normally would.

basically your cutting off the back of the Ford bell housing and the original front off the transaxle and welding the front half of the ford bellhousing onto the back half of the Audi transaxle bell housing.

No, bellhousings are usually no-heattreatable sand castings.

354, 355, 356, 357

No worries

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 of 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.

Should they be V-grooved?

Ed Huntress

Do you mean these alloys CAN not be heat treated or that they typically ARE not heat treated?

correct me if I'm wrong, but I believe these alloys can be heat treated

300-series aluminum castings sometimes are heat-treated to T5, T7, or, rarely, T6. If they heat treat transmission casings, most likely it's to T5. But they may not be given an artificial heat-treatment at all, in which case, I think, they revert to natural aging, which (again, I think), is T2. I could look it up if anyone cares.

But there's an implication in this thread that the consequences of welding heat-treatable aluminum may be something like those of welding heat-treatable steel. Not so. They're so different that you don't want to make any comparisons. As Ernie suggests, it doesn't have a lot of influence on weldability in aluminum. The characteristics that make some aluminum alloys, such as 2024, difficult or impossible to weld, are not related to their heat-treatment properties.

Ed Huntress

It would be hard to give an accurate answer without *knowing* which alloy(s) is(are) involved. Here is a link to some likely candidates along with weldability rankings.... some more weldable than others...

Ack, I stuck my foot in it by using 2024 as an example. Actually, 2024, in addition to having some other problems with welding, *does* share some of the problems with steel. Its hardening mechanism does include a quick-quenching function, so it can produce a hardened zone around the weld that has little ductility, which contributes to cracks. Most other alloys don't harden by quick-quenching.

I'd love to clarify this but aluminum is a complex material when you heat it, by welding or otherwise. The heat-treatable alloys actually do stress welds something like steel when they start in one particular condition: T6. Otherwise, they generally don't. The big problems are hot-shortness that is more common with the heat-treatable alloys, and, in the case of 2024 and some of the 7000 Series, migration and agglomeration of alloy components by means of diffusion. It makes the area around a weld quite weak when it's still hot; thus, cracks.

Nobody probably cares, but I hate to give misinformation.

Ed Huntress

I'm not making myself clear.

Maybe I should ask more directly.

I'm not worried at all about weldability, that's not my question.

My question is does welding trans cases result in a weaker assembly. Specifically, if the case is heat treated from the factory doesn't welding negate that treatment and return the alloys to unhardened condition in the area of the weld?

And I'm not talking welding up a crack from road debri, I'm talking a joint all the way around the assembly near the back of the bell housing.

So then I would need to know the alloy and is it heat treated from the factory?

Another question I would have is, isn't the piece only as strong as the alloy of the filler being used?

so what is the purpose of the slow cooling?

Prevents the welds from cracking by cooling too quickly

It should be one of your questions.

As others have told you, cases and bellhousings normally are *not* heat treated by the factory. They're normally designed to be strong enough for their purpose *as cast*.

If for some strange unfathomable reason these particular parts are

1) made of a hardenable alloy, and 2) have been heat treated at the factory, then welding will temporarily return them to the annealed condition.

But note that heat treatable alloys will age harden over a period of weeks or months. A deliberate heat treatment can hasten this process, but the schedules that have to be followed aren't something you'd want to attempt in a home workshop.

So if you're paranoid, simply set the finished assembly aside for a few weeks to let it age harden. If it is an alloy that does harden, you're good, if it isn't, you haven't done any harm, just wasted some time.

That might bring you some peace of mind. Obviously, you aren't willing to accept the answers being given here.

No. Welding isn't applying hot glue. The welding process produces a new alloy in the fusion zone that consists of the elements of the parent materials, and the elements of the filler rod used, alloyed into some composition that's partly dependent on the exact technique used to make the weld. The result can be weaker, stronger, or the same strength as the parent metal or the filler, depending on factors that you say you don't want to know about, ie the weldability of the parent alloys, and the procedures followed to accomplish the weld.

Gary

thanks for correcting me then

Contrare, I'm just trying to learn and thought I wasn't asking my questions correctly.

Having more of a background in the wrought aluminum alloys and not the cast I just took it for granted that the use of hardening in the process was more common than not. That was the premise that my questions were based on. I stand corrected.