So, the mainshaft is built, welded, sleeved and welded again, I thought the best thing to do was harden the shaft again, which I managed with my mini furnace and oxy-acetylene.
Then I put the shaft on the lathe and ran a clock across it...50 thou out of true, I couldn't believe it, so I thought right, I shrouded the lathe bed in sheets of asbestos (or whatever the healthy equivalent is these days) and set about truing up the shaft and got it to with 2½ thou across its length, which was better than a spare standard shaft I had so I assembled the box.
Gave the shaft a spin and it looked great, it looks plenty strong enough and is as straight as I'm going to get it, last night I assembled the selectors, detent springs and balls and checked out the overdrive and everything appears to be fine, with all pumps, seals and bearings looking good.
After making up a set of gaskets I mounted the overdrive and although it required a bit of gentle pursuasion with a hide mallet for the last ⅛", which was a bit of a worry, but after bolting everything up, everything turned, so let's see what happens. Oh and I've left the manufacturer's marks on the box rather than paint it, because I like things like that.
Sunbeam Alpine overdrive guru John Roseby will be havig kittens, but I had to give it a try! Anyway here's the box fully assembled and ready to go in, now onto the back axle...