Well saved John, a tricky job indeed. An unusual materials couple for a designer to choose, as aluminium is anodic to brass/bronzes and the corrosion you found was inevitable. Suitable application of Doubleboost required!
Thanks again for helping me out with it John. I got a tap to clean the threads, will work out fine. Differential back in the car this weekend, thanks. As someone below said, difficult to find a replacement -- only one company I could find listed it, but had none in stock. Not cheap neither for a scabby piece of aluminium.
You have done well John , Aluminium is a great material when new , but its a Bastard when something has a good few years on the clock and it starts to break down as a metal .
To anyone sitting on the fence in regards to supporting John on patreon, Ive been happily supporting him since he started his patreon page. The quality and the amount of content he makes available cant be beaten. Id highly recommend doing it because you really are getting value for money, especially compared to other larger youtubers.
That was good. Once I did a similar job. It was a position transducer in a hydraulic ram. I was able to set the piece up in the lathe. Then by boring incrementally I whispered the remains of the stuck transducer until just a thin shell remained. I could then unwind the thread. It unwound like an old helicoil does.
Its a bit late now but I've had good success using an acid that attacks brass but does not harm aluminium when trying to remove knackered jets from carburettors. The name of the acid escapes me at the moment but after 30 minutes the jet disappeared and the ali thread was perfect!