[leylandp38]

Well, I changed the Haldex oil and filter today, and reinstated the fuse. After a test drive to let the clean oil circulate, it is back to normal. No binding, even on a tight 3 point turn, all good.

I watched a few YouTube clips on changing the filter. As others have found, the drain plug was seized solid.. One of the best tips (in the comments) was to use the pump to evacuate the old oil and flush through some clean oil. I used alligator leads and a 9V battery.

The old oil and filter were filthy, it was clearly clogged, but I think I caught it before any serious damage occurred. I might do it again quite soon to guarantee a good flush. Now I know how it's done, it is surprisingly easy to do.