Gearbox casting corrosion!

[Andyvandy]

Having just removed the engine (AAZ) and gearbox from my 1990 Westy I thought I would give the gearbox a clean up as it was very mucky.
I decided to remove the end support bracket as it was very rusty and needed cleaning up and painting.

Having removed it I noticed that there was a build up of what looked like scale on the back of the casting where it is in contact with the support bracket.
Much more worrying was finding that around the top edge of the casting the alloy had turned to grey 'mush' in two places!

It seems that electrolytic action between dis-similar metals (steel support bracket and aluminium casting plus water and salt) had caused the aluminium alloy casting to corrode badly to the point that it had become porous.
I noticed this after removing all the 'mush' and having laid the gearbox down oil started leaking out of a small hole that had developed in the casting.

It is obviously not an easy thing to check whilst the gearbox is in the vehicle, but worth bearing in mind/consider checking when the opportunity arises.

These castings do not take kindly to TIG aluminium welding, so be warned!

Andy

[Oldiebut goodie]

Sure that the oil wasn't coming out of the breather hole in that end?
You must have missed the thread earlier (this year?) - several of us posted about this (including the gearbox guru Aidan) yet others said it can't/doesn't happen. You didn't happen to take pics of it did you?
I have had the same on engine mounts in a boat - rubber/ally of some sort/steel bolt in salty atmosphere and they end up with just the grey mush (good description )holding them together.

[Andyvandy]

Oldie,

The oil was definitely coming out of a hole in the casting not the breather.
It definitely does happen!
Unfortunately I didn't take a photo, I am so busy just getting the van back on the road so we can drive it to France (where we are moving to in August). I just don'thave the time.
I didn't catch the earlier thread..

Andy

[Oldiebut goodie]

Are you sorted? - I have a good one here from my old 5 speed box if you need it. I doubt that my nose will go to mush before I or the van go to meet their maker!

[Andyvandy]

Oldie,

That would be great!
I have 'fixed' the problem in the short term but would prefer a good solid casting.

Please PM me cost etc.

Thanks

Andy

[Oldiebut goodie]

Check to see if the part no. matches up - this is 094 301 211.
1 bolt missing!

[pionte]

I can confirm that it definitely does happen, this is the state my bell housing was in when I removed it ! I would urge everyone to add another earth strap directly to the bolt securing the starter motor.