V12 5 speed conversion - simplyperformance Simply Performance has been supplying V12 5 speed manual conversions for over 10 years. We have sold over 150 kits. Mainly this kit is used to convert the ancient GM400 3 speed box fitted to the XJS V12. This kit can also be used to convert from 4 speed manual to 5 speed manual. We supply a complete nut and bolt package to convert to manual. Jaguar XJS Transmission | eBay Find great deals on eBay for Jaguar XJS Transmission in Complete Auto Transmissions. Shop with confidence. Skip to main content. This quality used transmission has 95935 miles on it. M.T. Stands for a manual transmission and A.T. stands for 1990-1992 Jaguar XJS v12 Automatic Transmission 110k OEM (Fits: Jaguar XJS) $950. Buy It Now.