How can I seal a crack in my manual transmission housing?

Dear Car Talk

Dear Car Talk | Aug 01, 1993

Dear Tom and Ray:

Several years ago I had some work done on my 1979 GMC pick up that involved removing the engine and the transmission. After the work was completed, I discovered a puddle of gear oil forming in my driveway where the truck is parked. I traced the leak to a two-inch hairline crack in the cast iron of the manual transmission housing. My guess is that they dropped it. I've tried to seal it with several types of sealants, but have only been able to slow down the dripping, not stop it. Other than screaming at the mechanic, what else can I do?

TOM: You could do your whole driveway in gear oil, Mike. We understand it's the new look. Or you can weld the crack.

RAY: Right. Not only to stop the leak, but also to keep the transmission case from splitting in half. Under extreme load someday, like when you're trying to pull your mother-in-law out of a snowbank (with or without her car), the transmission could actually break apart.

TOM: So what you have to do is have somebody "bridge" the crack. They can put a piece of metal right across it, and weld that piece electrically to the transmission case. It's not very expensive, and can be done with the transmission still in the car.

RAY: It'll be as good as new, Mike. We've used this method on my brother's head on several occasions.

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