Back in 1996 I stripped my gearbox to replace bearings and restore synchromesh. Unfortunately whilst removing the rear casing I didn’t understand that it wasn’t just secured to the penultimate casing by four hex bolts and in trying to separate it I put a small crack in the casing.
The fifth fixing is a set screw (22 in the explosion below) and you need to remove the speedo driven gear and bush before you can access it.
I have lived with a small amount of leakage until today when I decided to swap the casing with one on my spare gearbox. I had great difficulty in removing the nut securing the rear drive flange on my spare and only got it off with the help of my local garage with their pneumatic rattle gun but that was not my only problem.
When I came to refit the speedo drive bush I couldn’t get it more than half way in. After much messing with heat and cold and putting a small chamfer on the bush and still failing, it dawned on me that perhaps set screw 22 was the offending obstacle. I had tightened it but not quite enough. After some more serious torque I finally got the speedo drive bush installed but this set screw is definitely my bete noire.