Transmission/overdrive problem??

Thanks for the responses and advice on my O/D problem.  I disconnected the
overdrive wiring and took it for a run today which confirmed that it was stuck
in overdrive, so I'll check out the solenoid next, because it was acting up
over the summer, and if that's not it I'll clean the operating valve.
Hopefully that will fix it,
but just in case, could someone tell me how I would know if more serious
damage has been done by forcing it in reverse.

thanks again
Barry