Maybe I should've cleared this up better sorry
What I really meant was if the steam locomotive had something wrong inside but was not the boiler. The driver
The "driver"????? Please, you must be new at this. He/she would be the Engineer. The term "Driver" on steam locomotives, is generally used throughout Europe.
could stick the engine into neutral, power off, and do his best to keep it moving before something else bad happened.
Nope. Shouldn't do that either, as without lubrication carried by the steam flow to the valves/cylinders, both would subsequently be damaged. Also, the running gear on steam locomotives do not like to be in "neutral" while moving.
But if the Diesel stalls, then a steam engine like the 844 can help its 100+ car train slowly but easily.
That was only one unit that had a grounded traction motor, on that freight train. Also, with 844 pushing on the rear, we got the train speed back up to about 20MPH.