vauxhall astra f17 gearbox damage

my son friend bought a new gearbox for his car and left the old one here I decided to investigate what went wrong humm
Big hole in the aluminium casting and guess what I found

[@ChrisPatrick-q6k]

My uncle bought a 2003 Vectra 1.8 with this box new. He drained it at 5,000 and filled it with 75w/80 and changed it again with the clutch at 170,000. It's now on 280,000 and going strong, he thinks the factory GM fluid is the cause of these issues.

[@ChrisPatrick-q6k]

@@jw-pk5vf Interesting you've said that, I've just got some 85w/80 gl4-5 for my F17.

[@sjiroofingandmaintenancese2494]

I have this issue

[@welshman2011]

Rebuild it and sell it on

[@ashleyjones1976]

Big hole in the case it's handed it

[@stevemcilroy9518]

?