Cracked gearbox - possible repair?

[Mikeyplum]

It looks like I have cracked my gearbox, resulting in the slow, but sure expulsion of all of its fluids. The crack is invisble, but I have washed the area and can see the oil seaping from the cast.

Before I look into replacing it which will cost about £400 for a second hand gearbox with a guarantee and half a days labour for the removal and fit. I was wondering whether it could be repaired by welding it?

Couple of Q’s:
- Has anyone had experience of having a gearbox welded?
- Can it be done in situ, or would the box have to be removed?
- Does anyone know of anywhere in South Wales who would be able to do it?
- If welding is not an option, does anyone have £600 they could give me? (may be pushing it on that one )

The car is a 2002 VW Bora TDI PD130 (6 speed manual).

Cheers
Mike

[Monty Python]

Clean the area thoroughly then stick some J-B Weld over the crack.


Failing that, you'll need to Tig weld it.

[HustleRussell]

Depends how the crack ocurred- it may be indicative of a significant mechanical problem in the gearbox.

[airbrakes]

HustleRussell said:

Depends how the crack ocurred- it may be indicative of a significant mechanical problem in the gearbox.

This. Unless you've bashed it on the floor over a humpback bridge, something has gone drastically wrong inside to blow a crack in it. But anyway, for a semi-permanenet solution, chemical metal might work as long as you thoroughly clean (steam clean?) the crack and surrounding area of all oil.

[zcacogp]

HustleRussell said:

Depends how the crack ocurred- it may be indicative of a significant mechanical problem in the gearbox.

This. And the fact that the casing of a gearbox is structural and hence integral to it's operation means that a crack could have knock-on effects elsewhere.

May be a load of cash but replacing it seems like a good option ....


Oli.

[Mikeyplum]

doogz said:

If something inside had gone that catastrophically wrong to crack the case, he'd probably know about it by now.

The box is smooth as butter, like always. I drove it 6 miles home thinking the puddle under my car at work was engine oil (it was dark). I checked the oil level, it was fine and no warning lights on dash. Checked power steering, all good so drove home.

The likely cause is the it has been bashed on something. The car has been lowered by 50mm on Apex shocks and springs, however, I know when it must have happened and during that time I don't recall bashing it on anything. But it may just be my memory.

[Krikkit]

If it was cracked through impact damage you would be able to see something on the engine sump/gearbox casing to indicate it.

To get it welded you'd need to have the box off the car and stripped down anyway, no-one in their right mind would weld a gearbox that still has oil in it!

[Mikeyplum]

Krikkit said:

If it was cracked through impact damage you would be able to see something on the engine sump/gearbox casing to indicate it.

To get it welded you'd need to have the box off the car and stripped down anyway, no-one in their right mind would weld a gearbox that still has oil in it!

Could the oil just be drained out whilst in situ?

[McWigglebum4th]

To fix it properly you would have to remove the gearbox, strip it down, acid dip the casing, preheat the casting, the TIG the casting, possible heat treat and distress the casting, rebuild the gearbox and then finally refit the gearbox.

Not cheap

[CrutyRammers]

Mikeyplum said:

Could the oil just be drained out whilst in situ?

It'd still have oil coating everything, which will vapourise, which'd be somewhat dangerous when combined with very hot metal and electrical sparks in a confined space.
And you'd never get the surfaces of the crack properly clean in situ.
And depending on where the crack is, it might not even be possible to get a Tig at it anyway.

[HustleRussell]

doogz said:

If something inside had gone that catastrophically wrong to crack the case, he'd probably know about it by now.

Not nececelery, I've had a slightly dodgy propshaft bearing vibrate and fatigue a gearbox until a crack started to propagate in the tailhousing. Since it was a Caterham I could feel that something was wrong by the time the bearing was causing a vibration, but had it been a proper car with big rubber engine/gearbox mounts it might have not been so easy to notice.

[speed_monkey]

My main diff bearing worked loose on my 2000 Polo GTi (its a known issue and a fix is to replace the rivets with bolts) and decided to launch itself through the casing, draining the oil and lunching the box.

Is your gearbox whining???

Edited by speed_monkey on Wednesday 14th August 14:11

[IN51GHT]

JB Weld, clean & abraid well before applying

[vrooom]

Maybe driveshaft or some seal is gone? they can made proper mess.

[HustleRussell]

doogz said:

A slightly dodgy propshaft bearing is certainly a problem.

But it's not quite a catastrophic failure.

I never said it was / would be a 'catastrophic failure', but it did cause some not inconsiderable inconvenience, firstly driving the car home with smoke from burning gear oil bellowing out of the transmission tunnel, before removing the engine and 'box, replacing the bearing, re-installing engine and 'box, and then running the car for a few thousand more miles and several races with an increasingly bad gearbox oil leak (It would be sloshing across the passenger floor by the end of the race), removing engine and 'box again to find the mystery leak, stripping the gearbox once again and re-assembling it with a new tailhousing casing, putting it all back in the car etc etc.

What I'm saying is that if the crack is indicative of internal issues then spending furter money trying to fix the leak will be a false economy and a replacement 'box the better option.

If the crack was caused by something whacking the casing, then chemical metal is probably just the stuff.

[CrutyRammers]

speed_monkey said:

My main diff bearing worked loose on my 2000 Polo GTi (its a known issue and a fix is to replace the rivets with bolts) and decided to launch itself through the casing, draining the oil and lunching the box.

Is your gearbox whining???

Edited by speed_monkey on Wednesday 14th August 14:11

The main bearing is held in place by rivets? That's some cost cutting right there.

[speed_monkey]

CrutyRammers said:

speed_monkey said:

My main diff bearing worked loose on my 2000 Polo GTi (its a known issue and a fix is to replace the rivets with bolts) and decided to launch itself through the casing, draining the oil and lunching the box.

Is your gearbox whining???

Edited by speed_monkey on Wednesday 14th August 14:11

The main bearing is held in place by rivets? That's some cost cutting right there.

Its crap... worse design I have ever seen.

All of the cras are a ticking time bomb

[Rostfritt]

Anyone know what happened to this gearbox? Mine has a dodgy crack in it and lost most of the oil. I doubt it is worth welding it and I can't really afford changing it right now. I think some liquid metal stuff and keeping it topped up might be OK for now. I doubt anything has gone badly wrong inside, it is making a grinding sound in some gears now but changes fine in all gears. Any thoughts on whether this is a wise course of action?

[BritishRacinGrin]

If it's grinding now, the low oil has damaged the synchros. This is not going to rectify itself. However, if you can keep oil in it, the gearbox will probably soldier on for a while yet. Wait for the gearbox to cool completely, thoroughly degrease the area, identify the start and finish of the crack and then apply chemical metal or sealant as liberally as you like. You probably won't stop it leaking, but you might slow it down.

[Leptons]

You could used to buy this aluminium welding rod that you heated with a blow torch and it lowered the melting point of whatever you were welding and stuck them together.
I remember it being demonstrated at Autosport show one year...