Not sure about the 37s...
Mid to late 1980s, the early morning Glasgow - Oban was up to six or seven coaches, hauled by a single Class 37/4, no banking loco
The Saturday only Glasgow QS through service arrived with a Class 47, then departed with the same Class 47, with a pilot loco to get back up the hill
I'm sure I read a story somwhere about a 101 having to turn back several times
Not just once, but several times
Towards the end of their life it was quite common to see a first generation leave and then trundle back in "every body off"
The usual solution was for another DMU to couple up, then drag the offending DMU off to Eastfield, the second DMU would then come back
However, I do remember a DMU failing right at the entrance to the tunnel
It was pushed back into Platform 7 by the arriving Aberdeen service
Normally such an Aberdeen would reside there for nearly two hours, however it was quickly moved to Platform 2
The spare loco from Platform 1 (as it is now) then hauled the dead DMU up to Eastfield
The same DMU reappeared later that evening, but promptly failed and ended up dumped at the end of Platform 5