TR2/3/3A TR3 gear box dismantle question

[Adrio]

If one wanted to replace the main shaft on a TR3 gearbox, does one have to remove the layshaft (countershaft) first. The manual seems to have the layshaft removed first, but I am wondering if this is because it is assumed that the entire gear box is going to be dismantled. All I want to do is replace the main shaft, so do I need to remove the layshaft first?

 

[TR4MAN]

I believe so. It allows you to lower the lay gear out of the way. Make yourself a dummy shaft the same diameter as the lay shaft but just shorter than the lay gear itself. Put this in place of the lay shaft. It keeps all those needle bearings in place. Make sure you account for all the needle bearings between the main and input shaft.