I'm trying to troubleshoot no overdrive in a truck I recently bought. I checked with a test light at the plug going into the overdrive solenoid and verified there is power to it. Actually there was power to both large and small wires . I tapped into the small wire and ran it into cab with a toggle switch then to ground. Overdrive still doesn't work. So this indicates the solenoid is bad or overdrive unit is bad? Is there a way to test beyond this or is the next step to replace solenoid to find out what problem is? Where is a good place to get a solenoid and is it a simple install? Thank you