Welding Tips and Tricks

Has anyone welded a VW Beetle Trans?
I understand from VW forums they are an Aluminium/Magnesium alloy possibly AS21 or AS41.
Any help would be welcome
Thanks

Hi - I've not done a VW tranny - but many other gearbox cases with cracks in / lugs broke off / chunks knocked out of them ! - the biggest challenge is the amount of oil that the porous nature of ally absorbs over time - once clean enough the castings seem to weld faily well with any process available to you ( I've used oxy / acetelene - stick weld on DC - regular MIG & spool on MIG - only recently got an AC TIG but I think this would be better ) if possible & you won't want to hear this -but the casing wants to be stripped of everything - then soaked in any solvent you have - then steam cleaned - then heated in an oven if possible or with a large propane torch as evenly as you can - allow to cool slowly - wire brush area to be welded with a stainless steel brush - then repeat heating / brushing till no more gunk appears - now your ready to weld - pre heat the whole thing - make the repair then post heat to achieve a consistent temperature and allow to cool slowly. Wow that sounds long winded - but I done a load by this method & it works - the better qualified guys out there may disagree - but I just stick to what I find works. As you posted this in the TIG section I assume you have access to AC TIG - once clean it should go like any other weld - I would as a layman use 5356 filler rod but in the past I've used MIG wire that was either 4043 or similar & not had problems - weirdly the only problems other than oil contamination was cracking - often nowhere the repair which I assume was expansion / thermal shock so I used pre & post heat ( temperature range apply liquid soap & wait for it to turn very dark brown - like when your going to anneal it ) much like welding cast iron - I'm sure one of the moderators will give a more scientific comment ! Good luck.

Thanks for the great tips, you are right I was thinking of AC TIG welding it, my main concern is that the vw beetle engine and trans castings appear to have a high magnesium content and I am hoping that somone has had some experiance of that material in particular, thanks again.

Hey,

Jody has a video or two on welding mag.Use the search engine on the main WT&Ts page. Also google it and or welding VW trans to find some specific info.

Mick

i might be wrong, but 5356 might not be the best choice for filler. on a alcotec filler rod chart, 5356 is NOT supposed to be used for temps over 150 degrees F. i think 5554 might be the best choice. it shows on some alloy combo's a temperature rating. but... on 500 series alloys, wich should be low magnesium alloy, no rating for any of the 5000 series rods show a rating for "t" wich is temperture. if you look on other alloy combos, 5554 does have a "t" rating... so i would think out of the 5000 series rods, 5554 i think this would be the best bet.

Is it a magnesium or aluminum casting? Best way to check is to use vinegar. Magnesium will react when in contact with vinegar and aluminum won't. If it's mag you most common filler is az92 but there are others, best thing is to find exact make of the mag but 9 times out of 10 AZ 92 will work. With magnesium use a carbide Burr air grinder and groove out the crack and than clean with acetone. If it's aluminum casting I will usually use 4004 or 4043, there are a few others. These are good at high tempts and my at a lower.temp than 5000 series rod so they make welding castings easier and they have better elongation so they don't crack as easy. Aluminum castings can suck cause oil gets in the pours. Some go good some suck. My strategy is to groove out that crack, and clean with acetone. And try.welding, sometimes further cleaning is needed. the best.way I know is to baked out the oils in the pours a old grill works great for this or if you have a machine shop with a acid tank close by that works great to. A could other things magnesium grinding dust and chips are extremely flammable so don't out the crack and than use a cutting torch. Preheat and post.heat helps on both to avoid cracking. Usually like 200 degree preheat and the post heat varies depending on the alloy. You can look it up with Away.

As per the cracking issue, and if it's in the middle of the gear case instead of an edge, if there is no issue with clearance, it is sometimes better to weld a band aid over the crack made from 11 gauge. Drill a crack stop hole at each end of the crack. It lessens the chance of further cracking, and allows you to weld to the outside of the case where oil hasn't been soaking.

when possible, i have had the best luck grinding out the crack all the way through. adding in all new metal. of course this isnt possible in all situations. i start by drilling the ends but many times after you light up on it, you will find the crack continues.

the transmission cases do have a large amount of magnesium in them..

The problem I have seen is corrosion from moisture around the welded area after a few years exposure.. We use lots of salt on the roads during winter.. It makes the area around the weld get white and fuzzy. I have used 4043 or 5653 without incident.

It would be best to match the case to the rod but these were simple repair jobs.. Hole in case, crack from road Debris etc..