QuestionIm working on a 1955 ford customline I am not sure how the overdrive is operated their is a eletrical sw on the floor and a cable under the dash would you please discribe the proper operation and how it is hook up , thank you bruce
AnswerThis is a tall order: The overdrive system is complex, and has many switches, a control relay, a speed sensor, a solenoid, and 3 operator controls.
You really need to get a shop manual for this car - it will describe how to operate the overdrive, and how to repair it, and include a wiring diagram.
I'll give you a brief run-down:
The cable is the lockout device. When you pull all the way out on the handle, the overdrive ceases to have any function - you can just drive the car as if it doesn't have overdrive. You should only do this when the car is completely stopped, and it pulls out much easier if you put the shift lever in reverse before you pull out the handle.
When you push the handle all the way in, the car will drive normally except that up to about 25 MPH (you'll hear a click), the car will 'freewheel', in other words, if you let off the gas, the engine will idle and the car will coast, with no engine braking.
With the handle all the way in, if you drive faster than that, when you lift off the gas momentarily, the car will shift into overdrive, which slows the engine down about 30%, saving gas and wear on the engine. If you slow down below about 20, the car will automatically shift out of overdrive, and freewheel again.
If you floor the gas pedal, at any speed, when you are in overdrive, the car will automatically shift back to direct drive, the engine will speed up, and you will get faster acceleration. Once this happens, if you keep your foot on the gas, you can now pull the handle back out to lock out the overdrive, but this is a tricky maneuver to master, and I don't advise it except in an emergency (like you just realized you are about to head down a steep hill, and you need more engine braking).
When you have to back the car up, the shift lever automatically locks out the overdrive (because the overrunning clutch in the overdrive prevents driving the car backwards).
All of these functions are controlled by the devices listed above - and it's beyond my scope to try to give you the complete schematic and specs for them - get the shop manual and learn about the system.
This is one of the most sought after accessories on old cars - it improves the car immensely for highway useage, and saves fuel, noise and wear. Around town driving isn't affected much - although you get a little better acceleration than a non-overdrive equipped car, due to the higher rear axle ratio used on overdrive cars.
Dick
