Best approach to repair gearbox lug

[Paulbarrett]

Have this to repair.
Would it be advisable to leave a bolt in and build up the area or leave out drill and re thread?

All advice appreciated

 

[harveyp6]

Did that happen when it was on the engine stand in the background?
If so that must be a bitter pill to swallow.

 

[BrokenBiker]

I assume you don't have the broken off bit?

If not I would be putting a stainless bolt in there, then giving it a pass just hot enough to melt the ally so the AC can suck any gunk to the surface, then clean it back with a die grinder and then start getting after it with some filler and build up over the bolt.

If you don't have a stainless bolt, show that black one the wire wheel and clean everything back to shiny steel to prevent any contamination being sucked into the weld.

Probably want to tickle it with a blow torch as well depending on what power you have at hand to weld it with

 

[Paulbarrett]

I know I’ll need to pre heat a f

Did that happen when it was on the engine stand in the background?
If so that must be a bitter pill to swallow.

no, been like that since the guy built it before me. 15 years or so

 

[Paulbarrett]

I assume you don't have the broken off bit?

If not I would be putting a stainless bolt in there, then giving it a pass just hot enough to melt the ally so the AC can suck any gunk to the surface, then clean it back with a die grinder and then start getting after it with some filler and build up over the bolt.

If you don't have a stainless bolt, show that black one the wire wheel and clean everything back to shiny steel to prevent any contamination being sucked into the weld.

Probably want to tickle it with a blow torch as well depending on what power you have at hand to weld it with

Ah yes stainless bolt, I’ll have one for sure

 

[Paulbarrett]

Tore it down for a refresh and a turbo.
Auto gearbox going on too

 

[Pete.]

If you weld over the bolt it'll shrink onto it when it cools and you'll never get it out. I once managed this by turning a tapered smooth plug from stainless and that came out but it was touch and go.

 

[Paulbarrett]

Build thread on here, commodore with bmw lump

 

[Paulbarrett]

If you weld over the bolt it'll shrink onto it when it cools and you'll never get it out. I once managed this by turning a tapered smooth plug from stainless and that came out but it was touch and go.

Remove whilst hot?

 

[Pete.]

I think that what I would do is get some ally bar in the lathe, drill the centre of it out perhaps 5mm diameter, turn a thread into the outside , fit that into the half-thread that you have there then weld it all up over the top. When you're done you'll have a guide hole to drill out and tap a new thread in. If it chews up the original thread just drill it more and bang in a 2D helicoil.

 

[harveyp6]

I know I’ll need to pre heat a f

no, been like that since the guy built it before me. 15 years or so

Well at least that's not unexpected.

 

[zzr1200]

Do you have a bellhousing or splash/backplate to confirm the bolt location, available????

Bolt diameter 8mm/10mm and pitch???

 

[Smallfry]

A BMW block will have a stainless location dowel there. Could you just position the dowel, then build up the lug, then either leave the dowel in situ, while redrilling for tapping size, using another bush to centralise, or crush the dowel down to remove ?

Or being a BMW block, would it be easier to get a replacement as there are loads available

 

[Paulbarrett]

a jig has been suggested which I reckon iOS the way to go. just fill it ups and re-drill and tap

 

[8ob]

There is room on that block to machine/mill the damaged area flat, bolt down a new lump of steel and redrill/tap that to accept the bellhousing bolt.
Just thoughts.

Bob

 

[Fazerruss]

The strongest method is to just take out the bolt, fully weld up then drill and re tap the thread.
I do hundreds of repairs of this nature. Not had a failure yet.

 

[zzr1200]

I'd be inclined to weld it up and re-drill, personally.