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Diff mount bolt snapped


gadget

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I went out to change the rear diff mounts today.

Had the rear two swapped in about 20 minutes. Came to unbolt the front and got two bolts out and the bottom M10 in the diff snapped.

Plenty of thread left so i thought i'd weld a nut on and it would extract easy enough

After far too many hours of trying i've given up for today. I've tried heat, freeze spray, plus gas and welding nuts on.

Two of the nuts snapped off more of the bolt :o

Anyone have any other suggestions of how to extract the bloody thing? It's a 10.9 grade bolt so i'm not looking forward to having to drill it out :ph34r:

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if you have access to some flat bar, say 5mm thick or so say 6 inches long and inch or so wide drill a hole in it same size or tiny bit bigger than remains of bolt.

slide plate onto bolt in hole and crank welder up to full and weld on solid.

now tap back and forwards a bit at a time to crack rust/hold and see if you can get it moving.

gives you a chance to put some serious heat into it and then shock loading it.

all depends on clearance as i dont know what space is available but seen blacksmith use this to free broken bolts that are just above flush into a hole, with big welder you can get mega heat into it.

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When i had the nuts welded on i was using a breaker bar to waggle quickly back and forth to shock it free. Same principle as the plate i would think?

Like the idea though. I'll dig out a piece of scrap bar and give that a try.

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Thinking about this...

I can strap a piece of flat bar along the length of the threaded part of the diff casing.

I can then weld all the way along the flat bar and the heat should be transferred to the casing.

Sensible or not?

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think the idea was a lot of local heat on weld, so transferred down bolt well and the tap back/forward could be tiny or proper hard.

wish i had asked blacksmith why flat bar instead of a nut but he is very very good so must be a reason. perhaps cause with bar you could see if bolt was moving or weld was failing and add more as requred, maybe saved on the breaking bits off, not sure.

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A proper engineering shop will sell you a 'reverse threaded' drill-bit [designed to be run anticlockwise].

Drill a small depression in the snapped bolt with an ordinary drill-bit, then fit your reverse-thread bit and switch the drill to hammer-action.

Then go for it! Use lots of pressure! Each time the drill-bit 'bites' into the bolt, coupled with the hammer-action, it shocks it just a little more loose. Trust me - it works: I used this method to get the remains of sheared studs out of a Lister stationary-engine that had spent its last 40 years in a collapsed and roofless cowshed.

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No matter what i've tried nothing will shift the bolt remnant. Can't get to it with a drill or grinder in situ so i'll have to take the diff off.

I suspect i'll have to remove the diff pinion too to be able to drill out the bolt.

What a pitfa for something that's supposed to be a simple job of replacing the mounts. :angry:

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CW: I don't know anyone local who has a TIG. That's superb control in that video. Very impressive.

BUT...

IT'S OUT!!!!!!!!!!!!! :i-m_so_happy::im-ok-smiley-emoticon:

Took the diff out and used Davie's smithy suggestion. Wound the arc welder up to 11 and welded a flat bar to what is left of the bolt.

Once it had welded to the bar i used the rest of the rod going over and around the stud to build heat.

Each time is snapped a little more of the bolt off when it let go and by the final attempt the bolt was pretty much flat with the face of the hole.

It took 4 rods but now all i have to do is run a tap through the threads and it's ready to go back it :)

Now, as the diff is out and the drive shaft seals have been disturbed should i replace them before i refit or should they be ok cleaned up?

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thats great news you got it out, sure sounds like it was a pain of a job.

Definitely a pain. Thanks for your tip :)

Glad you sorted it, heat and bloody mindedness are the key :)

Some of these "quick" jobs nurture bloody mindedness :)

After running a tap through the holes everything seems fine. Decided to pick up some new seals tomorrow and replace them whilst it's off.

The top four M10 holes are blind and the bolts for those are very clean. The front two holes are through and i suspect that the water and road salt gets in the back of the threads and rusts nicely. Any mileage in filling the rear of the through holes with silicone?

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Surely threadlock should also prevent salt and rust siezing the bolt, obviously depends on which grade of threadlock you use as to whether you can get the bolt out again as there are permanent and semi permanent grades. If it had threadlock originally I'd use it again.

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You probably need to thread lock the hole, not the bolt. Normally you gunk the bolt thread, which locks it, but the end exposed threads are wiped clean as you wind it in. gunk the thread up the hole, and the very end of the bolt is sealed.

I've considered cutting up a bolt to make plugs before. Never tried it.

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Surely threadlock should also prevent salt and rust siezing the bolt, obviously depends on which grade of threadlock you use as to whether you can get the bolt out again as there are permanent and semi permanent grades. If it had threadlock originally I'd use it again.

The original bolts have the threadlock on them from land rover. It's about the size of a thumb print on the bolt. Holds the bolt ok but is pretty poor at sealing.

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You probably need to thread lock the hole, not the bolt. Normally you gunk the bolt thread, which locks it, but the end exposed threads are wiped clean as you wind it in. gunk the thread up the hole, and the very end of the bolt is sealed.

I've considered cutting up a bolt to make plugs before. Never tried it.

I had considered the bolt plug. There are 4-5 threads remaining that could be used.

I think i'm going to go with thread lock the bolts and black gutter sealant in the open end on the hole.

The gutter sealant is pretty good as a sealant and it never truly sets.

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