I am looking at the WSM and I see this line in the transmission id section, "NOTE Gearboxes up to the serial number 2100 reported the complete engine power unit number along with the identification number." This is the only mention of the term 'engine power unit' in the WSM. Does anybody know what is all contained in the engine power unit? Is it the engine and transmission? I am interested because my gearbox serial number is under 2100.