[PDF] Opel GT: Conversion to 5-Speed-Getrag-Transmission control the height of the transmission based on a comparison measurement from the stock-GT. Transmission rear cross member Drive shaft The tail-shaft of the 5-speed transmission is larger at the rear than the original manual transmission. It closely matches the Opel automatic transmission tail-shaft. Unfortunately,[PDF] Converting GT to 4-Speed Manual Transmission for the other guy who drives another GT transmission type. While most conversions are from the 4-speed manual to the GETRAG 5-speed manual (which was well- covered in the August 1995 OMC Blitz issue), there are still numerous inquiries from those who inquire about swapping among the stock Opel transmission types.