To resolve the problems with the boiler alloy St 47 K-Mo that got brittle over time, the Reichsbahn had to fit its class 50 locomotives with new boilers. So they designed a new boiler based on that of the classes 2310 and 5040 and fitted it to 208 locomotives of the class 50 between 1957 and 1962. The rebuilt locomotives were called class 5035 and the same boiler was later also use on other Reko classes.
Many locomotives were also fitted with a Giesl ejector. Between 1966 and 1971, 72 were converted to oil firing and called class 5050. They were not only used for freight traffic, but also on commuter trains. The last steam-hauled standard-gauge passenger train in the GDR was hauled by 50 3559 in 1988. One year later, the last 5035 and 5050 were retired from regular service. Today, a two-digit number is being preserved. 