"The 3645 is in the 3600 series which included the 3630, (Perkins 6354 engine) 130 hp 3650 (Perkins 6354 engine 150 hp), and 3680(Valmet 180hp engine) Those are the early models and the 3635,45,55,70 and 90 late models with Perkins 100.6 engines and larger Valmet engines all 3600 tractors had 7800Kgs lift on the arm and were a very strong tractor ahead of their time with electronics. The 3645 is 145 hp and uses the 100.6 Perkins 6000cc engine, it has the legendary Dynashift transmission, all 3600 series tractors came with the first Datatronic systems as standard which monitored forward speed, Pto speed, fuel used, wheelslip control, rpm etc"