Duane - yup, had a loose connection at the solenoid. Fixed that, and now the thing works - partially. Go along, and it just pops out of overdrive - light goes off - I think it may be something loose that is affected by bumps. Wires look O.K., but I am guessing one of two things - either relay (easy to get to - relatively), or the wires to solenoid (or elsewhere) are bad (a bit of fun to troubleshoot). I will perform the test you recommended (got it today - thanks for the quick feedback!). I will also take a hack at the relay tonight - I am looking for broken wire connections, etc?

Thanks for the assist - I will let you know of the outcome.