My Hymer motorhome has a 2.8 TD engine with the 5 speed gearbox with the 5th gear added on outside the main gearbox. I am told this gearbox was carried over for a time into the 2.8 JTD engine range as well. As these ratios are not suited to my towing application does anyone know if or when this gearbox was replaced with an integral 5th Gear within the main gearbox unit on the 2.8 JTD engine.