broken bolt

I broke a bolt off removing a final drive from my super a. It is in the transmission casting and drilling has been unsuccessful so far. Any thoughts? What size tap will I need to run after(if) I get it out. Thanks.

If there's any stub at all protruding, welding a nut to the stub and allowing it to cool has always worked for me. The heat of the weld causes the bolt to expand and stretch the surrounding cast slightly. When the bolt shrinks back down, the rust breaks loose.

Mark, if it's one of the bolts that hold the shaft housing to the transmission case, those should be 7/16" NC.

Not sure how you're equipped, but there's about a half a dozen basic ways of attacking that bolt.

If you can weld, there's a lot of success to be had welding a good nut to the stump of the bolt and using the nut to turn it out. The heating and cooling involved with the welding will help to loosen it, too.

If you're not equipped to do that and can't find anybody to help you do it, then you'll have to go at it by drilling to some extent. Best general advice I can offer there is to get hold of some left-twist drill bits. A good hardware will have a small set that will have sizes enough to work. That left twist with the heat generated from drilling will sometimes break them loose, so use a left twist bit for any drilling you do. Whether you wind up drilling it out completely, or just enough for an EZ Out, I'd suggest starting with smaller bits and working your way up. The repeated heat and CCW torque may just break it loose in the process. In any event, do everything you can to keep your bit centered and running straight in. If you can do that, a 3/8" bit is about the largest you can go without drilling out the female thread along with it.

You'll get a lot of opinions about E-Z Outs -- some brands are better than others, some folks don't like any of them and I can't really blame them. They're VERY hard and if you break one of them off in the hole, you'll have a brand new problem.

I've had good luck with a gadget called Drill-Out. Comes in a set, mine were from CarQuest but Sears and other sell them. Basically it's a threaded mandrel with a drill tip on it that resembles a self-tapping screw -- left hand twist, of course. With your drill in reverse, the tip cuts the pilot hole down into the bolt. When it reaches a good depth, there is a second, tapered piece that threads down over the mandrel and bites the edges of the hole made by the drill tip. As it goes further, ridges on the taper fill and bite the edges of the hole. Some bolts will pop out as soon as the torque hits it with the outer piece, but it also has a hex head on the outer piece so that you an take your drill off of it and apply a wrench. I like them because they work, they're easy,and they're much less apt to break than an E-Z Out.

Anything you do should involve heat before you actually try to get it out. Try heating it with a regular handheld torch, propane is alright but Mapp gas is better/hotter. Heat it up well all around it once and let it cool. Heat it a second time focusing your heat on the bolt itself until it starts to turn red-to-yellow on the edges and let it cool. As that starts to cool, try applying a little of your favorite penetrant (PBBlaster, Liquid Wrench, MMO . . .). That does two things and works especially well if you still have a little thread or neck of the bolt protruding to help hold some of the magic formula in place. Start applying it while it will still sizzle and keep applying. It's cooling things a little faster and the shock will help to break up the corrosion that is holding the bolt fast, and as the corrosion crumbles/fractures and the whole thing cools, it will draw the penetrant into any gap. At that point let it cool down completely. Then just before trying your E-Z Out, Drill-Out or whatever, apply more heat to the tranny, keeping a little distance away from the bolt, the idea being to expand the outer part of the thread without putting so much heat to the bolt that it expands, too.

I've gone on long enough. All else fails a HeliCoil will fix her right up, but that's another discussion.

Thank you gentlemen for your responses. Your time and experience is appreciated.

Yer welcome! And please let us know how you make out.

I have also take out dozens by welding a nut on to the stub, even if its flush, seems the heat from the welding does the trick.

Good luck,, Let us know what happens.


Gene

If it's broken off below flush, weld a thick washer on first & then weld a nut on the washer. The washer is easier to get welded to a flush or below flush bolt than it is to weld down inside a nut. Just my $.02 worth.

If you are going to weld a nut to it use 7018 3/32 rod. No 6011 or 6013. Stronger weld and better control.