I have a canadian made 1.5 ton, 1947 AD. It has straight cut gears, no synchro at all. Its off the road for the full rstore so i have never driven it. When did SM420's come out? Mine has the pull up lever for selecting reverse. I'm told this was the pre-47 box, but I have bought another box recently locally (New Zealand) and they are both the same, and date codes are 1968 and 1962. Maybe the export models got the cheapo box.
Double clutching, as my Dad showed me: clutch in, gearlever to neutral. Clutch out, rev engine to match next gear (this gets the engine side of the box at the gearspeed that will be needed for the engagement). Clutch in, slap into gear, make it engage and dont pussy around. Clutch out. I had a '56 rover ages ago with no synchro in first, this was the process every time.
