My 7274 was purchased new by me in 1995 it was a great machine and I sold it in 2016 and it is still in use
The trans dipstick is where the poster said and be sure to check the level in the front drive axle as well...I just used a screw driver
I threw service manuals out for the tractor because...
The bang before the derailment sounded to me like a bad cushion drawbar collapsing instead of working as it should and it caused a good amount of slack "run in" maybe the engineman used the independent brake. But empty bulkheads can't absorb slack action when being pushed by shorter loaded cars...
Here is a picture of the relay starting issue fix.....
It does (did) work for mine a 7274 which was still going strong when I sold it after 21yrs of ownership good luck