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4L60E auto trans, cracked case in bellhousing area, can it be welded??

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Old 07-07-2003, 02:30 PM   #1
NASCAR314
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Default 4L60E auto trans, cracked case in bellhousing area, can it be welded??

Hello,
A stray bolt somehow found it's way in to the bellhousing area of my automatic equipped 96 Vette and came loose at high RPM's during an autocross and while bouncing and banging around, it put a small hole (about half the size of a dime) and cause a crack to develop about 4 inches long and vertical in the side of the bellhousing part of the trans. case.

Can a trans case like this be removed and welded up by a competent aluminum welder and reinstalled without destroying the internals of the transmission?

The bolt fell out upon removal of the cover under the torque convertor.
The bolt did NOT originate from anyplace in the bellhousing area such as front pump bolts or torque convertor bolts. Where this expensive bolt originated is a mystery that may never be solved. (Black bolt, metric, about 1" long with about an 8mm hex head, pretty small bolt)

Any aluminum welders out there?
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Old 07-07-2003, 03:16 PM   #2
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (NASCAR314)

I had my old 700R4 in my Irocz welded with no issues at all.

It had a 5" hairline crack near the top of the case.

vic

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Old 07-07-2003, 03:20 PM   #3
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (NASCAR314)

Yes... Usually you'll need to put a little heat in the thicker castings to get a good weld though. An oxy rosebud flame will usually do the job. 'V' out the crack (all of it) and cut a short perpendicular line at the end of the crack (this will prevent it travelling further should it continue to crack. Then TIG it up or MIG it if you have a good one (or a spool gun); you'll probably have to make several passes to build it up enough and to provide enough strength. I had to weld an aluminum Honda oilpan the other day; same procedure...
-Jeb
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Old 07-07-2003, 04:56 PM   #4
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (jburnett)

Quote:
Yes... Usually you'll need to put a little heat in the thicker castings to get a good weld though.
Jeb,
That's what concerns me, will the heat warp things or damage any seals inside?
The case on these is pretty thick aluminum, especially along the lower lip, the crack got to this thicker lip area and stopped.

I'm not the one doing the welding, I'm passing it on to someone competent (I sure hope he is competent!) I will surely mention veeing out the crack and cutting a perpindicular line at the ends.

Thanks,
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Old 07-07-2003, 08:24 PM   #5
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (NASCAR314)

You don't put THAT much heat in it... And it's just localized around the crack. An oxy torch with a rosebud flae passed over the area afew times will put enough heat in it... You're looking for 250-300F; that should be plenty to get a good weld.
-Jeb
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Old 07-08-2003, 12:12 PM   #6
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (jburnett)

Jeb, What do you use for filler rod with aluminum castings ? Do you do anything to prep the filler rod before welding with it ? I can weld stainless and steel real nicely, but with aluminum I can get the puddle started but when I go to add filler I get a nasty crust on the surface of the puddle. The rod will melt back but the drop just won't join with the puddle.
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Old 07-08-2003, 12:54 PM   #7
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (SloRvette)

I use a 4043 aluminum rod; on thick castings like this you need at least a 3/32" or 1/8" rod. I always wipe my rods with a clean paper towel with some alcohol on it to make sure and get any surface contaminants off. TIG welding aluminum is very difficult; it took me almost 3 bottles of argon practicing before I got really good. The crusty contaminants that you're seeing are probably the surface oxides of the aluminum you're trying to weld. The material to be welded needs to be EXTREMELY clean and free of contaminants... I use either a stainless brush or a Scotch-Brite disc on a die grinder; only use them on your aluminum, other metals will contaminate them. Also, aluminum isn't like ferrous metals, you can't see the puddle develop, it just gets shiny; at which point you better add filler and MOVE the torch cuz 1/2 second later it will become porous!

Forgot: Get a gas lens if you weld aluminum and crank the argon flow up more; to around 25 or so (instead of the customary 18-20). A gas lens makes welding aluminum a lot easier and the welds a lot cleaner; particularly if you're just learning to weld aluminum.
-Jeb


[Modified by jburnett, 5:56 PM 7/8/2003]
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Old 07-09-2003, 10:52 PM   #8
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Default Re: 4L60E auto trans, cracked case in bellhousing area, can it be welded?? (NASCAR314)

Up-date:
crack went damm near all the way around as a hairline crack. had it ground out to a "V" and welded up by a racing shop, both inside and outside. Should do the trick!

Bolt came from the "Rear crankshaft oil seal housing", it is located behind the flywheel on the LT1 motor. Very hard to see with flywheel still on the motor.

My opinion is a lazy worker failed to tighten the bolt on the back of the motor wherever the LT1's are built. (I'm not knocking U.A.W. autoworkers :skep: )

Only 27,000 miles on the car, but still out of warranty :cuss
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