overdrive

[1969 modified]

I bought a 1965 chevy inline six truck to add to my stable. It gets along with my 69. The guy I bought it off of had installed a early sixties 3 speed standard tranny with a manual overdrive, but the overdrive linkage was never hooked up. I have put a manual cable on the overdrive and have switched it back and forth going down the road, but I do not notice any rpm change. The only thing I notice is the tranny "free wheels" when you let off of the throttle when it is in overdrive. If its not in overdrive then you can hear the load on the motor when you let off of the throttle. I do not have the electric solonoid hooked up on it yet. Does anyone have knowledge of how these overdrives are supposed to be hooked up or react. You would think that you would hear a rpm change.

Thanks