Crazyswede wrote:Jordan wrote:I think you could have a fairly easy shifting syncho-less box.. not sure though. I really think it depends on the # of dogs and the rest of the design. With such a small case to work with you need every mm of gear face (in my totally uneducated opinion) and synchros take up a lot of width...
The gearboxes in most offroad motorcycles are straight cut dog boxes. Of course the power, weight, and load ratios are completely different....but its very easy to shift them up or down without using the clutch and without grinding gears. Probably a lot more challenging in a car version. The big drawback to keep in mind with the straight cut gears is going to be the meshing noise. Probably fine for a race car but not something I'd want to listen to if I had it in a road car. I think the Mitsubishi Evo's run a Gemini gearbox that uses straight cut gears and they howl a bit.
The main concern I have about a synchroless c900/99 box is that the rotating mass of steel in these transmissions seems excessively high as compared to most transmissions and I just can't see even reasonably functional shifting happening that would work for a road vehicle. I suspect that's why the synchro rings are so large when compared to other transmissions such as a VW. Even the smaller 5th gear synchro would be a large synchro in other manufacturer's gearboxes. After giving thought to the need for such large synchros, my conclusion (right or wrong) is that they are necessary due to the massive cluster gear and relatively massive pinion/ring/differential combination to combat the kinetic energy present. It's really a wonder to me why these transmissions aren't stronger given that they seen to have twice as much steel as other transmissions designed for similar horsepower.