GEARBOX - Close-Ratio Conversion Pre-A+ Gearbox

As outlined in the 'Gearbox - standard production gearbox types' article, it is entirely possible to change the common 4-syncro gearboxes to the helical close-ratio set-up as used in the Cooper S, 1275GT, 1300GT, and some early MG Metros providing the right parts can be sourced. And you don't already un-knowingly have the close-ratio kit fitted! Part numbers are detailed at the end.

The other pre-requisite for this conversion is that it can only be applied to the early, pre-A+ type mainshaft gears. That's those that have the square-topped teeth as supposed to the distinctively pointed A+ profile. This is because despite being endowed with A+-type fittings for the mainshaft end and layshaft, the conversion gears have the pre-A+ tooth profile. This is not to say that the conversion cannot be put into an A+ gearbox casing - it can and is detailed in the relevant article.

What is essential to understand is that the pre-A+ second and third mainshaft gears are going to be