Big6
I had the same sort of not knowing issues when I finally got my O.D.
If you know how your cars engine RPM feels when running in 3rd gear now (O.D. not engauged), thusly when the O.D. is engauged and is functioning the engine RPM will be considerably lower when crusing in 3rd gear.
With the O.D. engauged starting off in 1st gear and shifting into second (above 27MPH) the car should feel at a normal engine RPM range/once you are in 2nd gear-simply let off of the accelerator pedal and the car will then automatically put itself into O.D. in 2nd gear.
This is when you will feel the engine RPM drop due to the O.D. kicking in.
Shift into 3rd normally and you will be in 3rd gear O.D. for hiway crusing.
Mashing the accelerator pedal to the floor when the car in in 3rd gear O.D. (or 2nd) causes the trans to momentarilly drop out of O.D.It feels like you are kicking into passing gear with an automatic trans.
If the O.D. is not functioning your RPM will not drop down and you will have to troubleshoot the system.
Check all of your wiring.My problem was I did not have a full 12 volts at the coil when running (I ran the O.D. circuit thru the ballast resistor). Once I had 12 volts at the coil all was well.
The wiring schemetic is simple.Just check all of the required locations for wiring continuity and voltages.
You could have a stuck solonoid which is easy to clean.
Hope this helps,Oldmics