About the heavy freight steam engine designated Ty37 which was designed to replace the Ty27.
The freight and coal train load sizes increased to the point that a more advanced heavy freight locomotic than the Ty23 was needed. The Ty37 was developed to satisfy that need.
Due the large number of Ty23 engines in use, the Ty37 never completely replaced it. In fact, relatively few of them were built.
It maintained the 1-5-0 axle arrangement that kept axle loads at acceptable levels.
The Ty37 was heavier than and had a more advanced boiler than the Ty23. That allowed for changes in the drive system that were also more advanced.
You can read a very detailed discussion related to these changes at this link.
All but one were scrapped. It can be seen at Lower Silesian industrial and Railway Museum
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