Still working through my '55 TBird.  Upgraded the engine using a '57 top end and totally rebuilt the brakes.  Car runs great, does not overheat, stops and I'm getting used to driving with my knees bent  (Ha Ha).  Now on to the Overdrive tranny.   This car has a Borg Warner T86 3 speed O/D tranny.   When I bought the car it had already been converted to 12 Volts, but the positive ground remained.  I switched the cables and reflashed the voltage regulator.  It's now 12 volt negative ground and all seems OK.  The generator light works and the battery charges.

I have been driving the car with the under dash O/D cable pulled out.   I tested the car for the first time today with the cable in.  I now have a tach in the car, so I can see if the O/D is working.  Here are my questions.

Are any of the O/D electricals voltage or polarity sensitive?  To get the car to shift into O/D my understanding is you have to totally let off the gas.  Should I be able to tell when the shift into OD occurs?  Is it a big drop in RPM or just a little?  I am just getting into the O/D issue at this point.  I can tell the engine is freewheeling, but I'm not sure the O/D is working as it's hard to tell driving around my neighborhood.  I have never driven an old car with O/D before so I don't know what to expect.