14 replies to this topic

[feeneymodo]

I had to replace a cracked flywheel housing. But when I was fitting the new one, one of the new bolts connecting to the gearbox casing sheared off.

https://photos.app.g...uM8T3PSMbAmyNk7

I tried drilling it out and rethreading but I have totally mucked it up. The hole is now a lot wider and I can't rethread it with my level of experience!

I've asked some local mobile mechanics about rethreading it for me, but all say it's too dodgy a job, because there's a risk they could drill into other areas of the casing.

I'm not sure what I can do. Can I leave it and rely on the rest of the housing bolts? Would this risk an oil leak?

Please no one say I need to replace the gearbox casing

Any ideas much appreciated!

[mini13]

Can you get a close up pic of it in its current condition?

Is the bolt sill in the Hole?

Edited by mini13, 31 August 2019 - 10:31 AM.

[feeneymodo]

Here's the culprit:
https://photos.app.g...LA3JGMaTM3LfxU7

Can't see much here, but after drilling I can now fit an M8 bolt down there :s
https://photos.app.g...51L5d2mbhutUdh7

[mini13]

OK, first thing I would do is remove the end plate and see what's going on down there,

[feeneymodo]

From all the drilling that I did, I think the remaining piece of bolt is gone, along with the threading.

[feeneymodo]

Good point, I'll take it off tomorrow morning and send some pics. Thank you!

[whistler]

Suggest you remove the transfer case and then sort out the broken bolt. It needs to be drilled out and either rethreaded or helicoiled. The thread is UNC and if you use a metric M8 bolt which is a finer thread you might pull that out when you torque it up. I had similar with a diff side cover bolt and drilled/tapped up a size UNC. Went from 5/16" to 3/8" UNC. All good now. You can fit a stud there instead of a bolt. Earlier engines used studs instead of bolts.

[nicklouse]

No idea what you are showing as you need to be signed in to see the pictures. Change your settings or use a host where the viewer does not need to sign in to see the pictures. Like imgur.

Which bolt hole is it as you can just miss it out in most cases.

[Tupers]

As it’s a bolt connecting the transfer case to the gearbox I wouldn’t advise running it without a bolt. The chances of it leaking oil between the casing is too high to risk having to pull the engine out again to do it properly.

You need to get the transfer case off to see how bad the hole in the gearbox is.
If you feel you’ve gone as far as you can go I would split the engine from the box (only a 5 minute job considering where you are now) steam clean it out and take it to machine shop and ask them to quote for repairing it.

If you’re lucky the might be able to tap it to 3/8 UNC and you can just run one odd bolt.

Do you know what grade your new bolts are and where did you get from?
A 5/16 UNC bolt isn’t the strongest thing in the world but it still takes a fair bit of abuse to shear one even with an impact gun.

[DeadSquare]

I recon that you'd get away with out it.

 

Because the subframe is tapered, the gearbox is in compression from end to end.

[feeneymodo]

Thanks for the help and advice! I took of the housing this morning and I hadn't realised how much I'd drilled away.

https://i638.photobu...&crop=1:1,smart

I've had to use a M10 bolt and having more visibility, I've done it properly for once.

https://i638.photobu...&crop=1:1,smart

The treading went well, I now just need to cut the bolt length down.

https://i638.photobu...&crop=1:1,smart

I wish I had taken my time and really gave it some thought before going all mad max on the problem. Oh well, live and learn!

I'll share pics of it refitted.

Oh, the bolts I bought new from Minisport. However, I think it was my misuse of the torque wrench that did it. I'm like a torque master now, feel like I could torque anything.

[Tupers]

Looks like you’ve gotten yourself out the woods, well done.

[mini13]

cool, my sugestion was going to be a helicoil to get it back to the right size, but if it was to big already ( it looked that way) then ths wouldnt have worked,

[Magneto]

Why are you using a metric bolt when all the others are English? Why not just helicoil it back to the origninal size or one larger as suggested - ie 3/8" course or UNC?

[Pete - W.Sussex]

I’m still amazed you could shear a bolt in the gearbox case - I thought the threads would strip long before that happened. Live and learn.