AEC introduced the Leyland Pneumo-Cyclic gearbox into their Mandators in 1969 as an option along with the 10 speed constant mesh splitter box (simply a 5 speed box with the 6th overdrive replaced by an air operated split on each main gear). The semi-auto box also had ten ratios with a splitter on each main ratio and was the same box as fitted to the Leyland Two Pedal Beaver. These boxes gave the same top speed as the normal 6 speed boxes but enabled more flexibility on climbs etc. These boxes were also used on the V8 Mandators but because of problems the semi-auto box was discontinued and withdrawn in 1971. AEC also produced their own 10 speed range change box and this was offered in replacement of the auto box in Mandators, not that many had been sold with that box originally. Again though by 1974 the AEC range change box was replaced by a bought in Fuller Roadranger range change box which was more cost effective. As for the Mammoth Major Eight I don’t believe the semi-auto box came as an option, as in 1971 two boxes were introduced both being 10 speed constant mesh splitter and range change gearboxes. Possibly the auto box in the video was one from a Mandator and not the original driveline. The semi-auto boxes weren’t as much a success in lorries as in buses (being the same box), the demands in road haulage being much more excessive, quite often the gearbox fluid temperatures would become extremely hot and damage would occur. Franky.