Due to the acute shortage of freight locomotives, the Reichsbahn undertook a thorough rebuild of the Prussian G 12. In addition to new boilers with a combustion chamber and mixing preheater, they received new cabs, a longer frame, new inner cylinders and Trofimoff valves. As a result, the locomotives could now pull the same weight as the class 44 on flat land, run faster and use less coal. The reconstruction of more than 200 locomotives ultimately failed due to the high costs and the shortage of materials in the planned economy. 