January 2012

Well I had to get things sorted out, the Plymouth Barracuda, much as I loved it was going to sit there for another 18 months before I could even make a start on it, so I decided to move the project on and concentrate on the Alpine.

Upgrading the car to overdrive spec, especially with the ridiculous cost of fuel these days was absolutely essential, but trying to track down a series 5 fine spline synchro overdrive gearbox proved to be more difficult than I thought, so with the help of my old friend Peter Wood, I had a rummage through the shed and found an overdrive, but then needed a mainshaft in order to fit it.

These are as rare as hen's teeth. I even spoke to Sunbeam Alpine Owners Club oracle John Roseby and he agreed, I'd need to buy a complete series 5 gearbox and overdrive to find one, which rather defeats the object!

So, I decided to build my own mainshaft. You need an early overdrive mainshaft, of which there appear to be plenty about as they were fitted to Rapiers and such, together with your Series 5 Alpine mainshaft.


You need to normalise the two mainshafts to remove the hardening, where you need to cut the mainshafts and machine them. Then with the aid of a massive vernier to check the length, I machine a spigot on one shaft and bored the other to fit, cutting a vee so they can be tig welded together.

I also machined up a sleeve, which will slide over the welded joint and that in turn will be welded the full circumfurence of the shaft in an effort to retain strength, while leaving enough room to slide the rear bearing nut over the top.

The next job will be to carefully "clock" the shaft to ensure it is absolutely true and then re-harden the shaft.

Whether or not this will work, I have no idea, but if it all goes tits up, I can always give John a call and see if he can sell me a recondistioned one! Stand by for an update...