Don't know what's going on here. Maybe even a different supplier.
The discussion I had with the guy at Rakeway said nothing about welding up the splines, which is a non starter anyway, from an engineering point of view, but actually re manufacturing the splined ends of the 2 items and then bead welding them back to their respective ends. IE crownwheel hub and transfer box main drive sprocket which are bead welded on now.
This method would definitely cure the problem but be quite expensive as a one off, as requires some accurate machining and a beadwelding machine but could become cheaper if we could get at least a dozen or so to do.
I don't know what the prices are that he has sent Brian as he hasn't told me. The method below I estimate at about £150. Their suggestion I reckon between 5 and £700.
However my suggestion was to use the existing splines, but with the 2 parts set into a purpose made machining jig and cut in 3 keyways. Make 3 keys to fit from moly van, weld them in with TIG. This would anneal the hard mat'l and not need re heat treating and then clean back the surface to original dia as there is a brg in the transfer box goes right over that spot.
I already made the jig and set the parts in their respective positions. The machining need not be perfect on 120 degrees (as it will always fit in one position.) I supplied the mat'l for the keys and to make 3 would only take about 1/2 an hour as they need to be a transition fit in their keyways.
Those were the options as I arranged with Rakeway, I am not aware of anything other than that.