cracks in aluminum transmissions

[nbyjim]

Can cracks in cast aluminum transmissions be repaired by tig welding?If they can what type of aluminum rod would be best? Thank you!

[Welder99]

Yes the crack can be repaired.Tig would be my choice.most transmission i have repaired seem to have a good grade of Aluminum.Ide go with 5356 filler.Pure Tungsten 15cfh.Pure argon.bevel out the crack and use acetone to clean.If the area to be repaired has been in touch with transmission fluid.U can also use oxy/act.tourch to preheat and that should burn out any oils that maybe soaked into the casting.once you fire up on the aluminum,you may find a black soot surface to the top.use a Stainless steel wire brush to clean.i hope this info is of some help.maybe if hawk is on line he can add some light.(hes a good ole boy and knows his suff. )....

[HAWK]

nbyjim,

Looks like Welder99 has you covered. The only thing I might add is use a carbide bit to bevel if possible. This will cut down some on contamination you will get in the casting from you grinding wheel. I used the tan aluminum rated grinding wheels, but they will still leave trash in your casting. If you do heat the casting to cook off some of the oils be ready to weld when the temp is about 300 degrees. This will give you a nice flowing filler and make the second/third passes (if needed) lay in better.

If you have a high pulse rate capability, crank it up. This will help float the casting impurities to the top.

[JWELD]

I have used the acid wash for the cases and a die grinder (Dremel is good or regular die ginder) with a carbide bit, also can use a "heat stick" to tell you when you have the right temp.

[HAWK]

JWELD,

The heat sticks are nice. I ran across a digital display, IR non-contact thermometer which is great for preheat temps and interpass temps as well. They are handy as a shirt pocket.

[H80N]

Guys
may be more conservative... but from older trans cases.. ran into a bunch that were porous... and will not do them unless completely stripped and degreased,,, are the newer ones better quality??? am I behaving like a fuddy duddy?.... I also have been in the practice of preheating the whole case to about 350-400 and kept them at that temp till cooked out... then covered with fiberfrax blanket over all areas that were not being welded... just leaving a window for the repair area....to keep even temp....concerns about warpage etc.. even cooling and strength of repair... without inducing stresses.. also.. did dyechem on cracks before to spot crack ends with UV light ... then drilled the crack ends... Then ground out to a vee.. before welding.... learned and started this practice in the 1970s.... U.S. cases were sloppily cast from what seemed like indifferent alloy and euro cases seemed to have a lot of magnesium... so needed a full gas jacketed environment.. so left those to the guys that did them all of the time..... refuse a lot of work on trans and transfer cases.. right now... am I allowing old prejudices to stop me from serving customers.. and make money???
Know I have been quoting way high on those because of past headaches..
sure would appreciate some input..
thanks
Heiti

BTW... tig a fair amount of aluminum castings... but have been a bit gunshy on trans cases because of old experiences......

[Welder99]

Heiti,
i agree with some or most of your responce.Maybe i should be a little more indepth.Most transmissions that i see are normally cracked in the Bellhousing area.either the motor mount or tranny mount broke putting the tranny in a bind or if the transmission was removed and they are reinstalling and tried to draw the trans,into the motor with bolts and cracked the tranny or ears.If the crack is in an area where the main body is at ide agree on tear down and yes complete degreasing.(as far as preheating the whole tranny i dont because the aluminum draws so much heat like a heat sink the arc itself from welding is a preheat.)and you also have to watch for over penatration inside the tranny if its in an area where machine work is present.as far as warpage goes.if the tranny is a complete tear down i can take a plate and drill holes and bolt it onto it to help the distorsion.the most part is to look at the tranny and see how much is going to be invloved verses getting another from the salvage yard,so you dont have a customer upset when u hand them a bill for move than a replacement.i have welded alot of trannys most i have found .GM>FORD CHRY.seem to have a good grade of aluminum.as far as inports...yes most are mag.or just plane junk.to try to weld.Tranfer cases i have had just as much good luck and good money in reparing.If this was cast iron ide look at it a little differnt.maybe more input into this subject can be helpful.i do enjoy this site,because its not just one responce.you get alot of people to input advise that others may not see.thank u for mentioning some of the other things that can be involved...
Welder99.

[H80N]

Welder99
thank you for your response... I may have been aproaching this with more caution than need be with more recent castings... and yep most breaks/cracks are in the bellhousing area.... was concerned that I was too cautious and overpricing myself... too many of my prospective customers want work done on trans in place in vehicle... locally it seems that ford truck automatic cases are broken at the starter,,, am not sure it is a good idea to mess with them in the vehicle... no matter how good the alloy... so I do not... but have many customers with AL cases for trans and transfer case that I have been avoiding.. because of my earlier experiences.... Yep I can repair a blowout in a transfer case where the chain has worn thru... typical of some late chrysler boxes... but will not even attempt without it being stripped of moving parts... can weld with 30a gun on the Trailblazer 301G on the back of the truck or back at the shop. with tig.....BUT... aluminum castings will walk around quite a bit when heated... and most of these are not able to be fixtured to maintain... flat where needed..... have done a bunch of the 4cyl Toyota 20-22r-re timing covers... cause the chain ate thru to waterjacket and on some to the ousside..... BUT... I built a fixture... to tie them down to to help maintain flat... and true the castings are thin enough that whatever warp they get may draw back down to the block as they get bolted down.. but being also a machineist... that scares the bejeebers out of me .... again sure would appreciate more input...
thanks
Heiti

[nbyjim]

Thanks for the info,I recently purchased a Dynasty 300 DX tigrunner and have started to do repairs for friends.I have done tig welding in the past,mostly with stainless and on older machines.The machine is bit much but with time I'm sure I'll figure out all that it does.Thanks again! cool site!!!