Overdrive

Unknown

I have the 37 terraplane deluxe coupe with the 40 power dome engine and transmission (The tranny has overdrive). I'm trying to sort the operation of the solenoid and cable mechanisms. My questions are 1. Does the solenoid engage the overdrive and the cable locks it out? 2. When I go to engage the overdrive is there a speed limitation (I don't see a govenor in the system)? When i engage the overdrive I'm guessing I will use the solenoid switch in conjunction with the clutch? When I use the cable control I'm assuming I will be locking out the overdrive. Do i use the clutch in conjunction with the cable? I don't want to just go and experiment. I don't know if it be damaged with improper use. It looks like it can. If one of you hudson experts could help I would appreciate it! Dennis

Jon B

Since the overdrive was not available in the 1937, one must ask: which overdrive do you have? Different years work somewhat differently from one another.



In general, the cable 'locks out' or 'enables' the overdrive. When pulled all the way out, the car will remain in conventional 3-speed drive. When pushed in all the way, operation of the overdrive is 'enabled' but you are not necessarily in overdrive.



When overdrive is enabled and you are driving around town in first to third gear, you are in 'free wheeling', which means the engine has no braking power. So if you plan to drive up and down some steep hills around town, be sure to lock out the overdrive by pulling the knob all the way out. Then, when you are driving down a hill, the engine will help slow you down and save your brakes.



With the knob pushed in and overdrive enabled, you can switch into overdrive above about 28 mph (this speed can vary) by simply raising your foot off the accelerator. There's a thunk, and you go from third to fourth gear. (Yes, there is a 'first-overdrive' and 'second-overdrive', but generally we are speaking of the overdrive you go into when in third gear.)



Now your car is in direct drive and you can also proceed down the road at a much faster rate of speed because your engine is turning maybe 30% fewer rpm's than if it were in conventional third.



Now you want to pass a slow truck, so you tromp the accelerator down. This switches the car to conventional third for greater power in passing. As soon as you're past the truck, lift UP on the accelerator and there is a thunk...you are back in overdrive (fourth gear).



So, the solenoid is used in kicking down out of overdrive, and the cable enables or locks out.



You use the clutch as you would in a regular car. Has nothing to do with the lockout cable.



You said you don't see a governor. If it's a 1941 or later overdrive the governor is a giagantic round electric switch that sticks out from the side of the transmission. If it's a 1940, there is no switch, the governor is integral.

Unknown

Jon Thanks for the info. I see it's all throttle activated. How Does the planetary system step down with a loading on the shaft? One would think that the step down solenoid would not disengage under a load. This car had no wiring in it when i picked it up. Where was the normal placement of the step down microswitch (on the carb, on the firewall, or on the throttle pedel? Thanks again for your help!

Jon B

Sorry, I hadn't noticed that you said '40 transmission in your topic starter. In '40 the kickdown switch was activated by a large washer mounted on the throttle linkage off the firewall; the effect was something like a foot-operated cymbal on a drum set. You wouldn't want to attempt replicating it on a '37 because, after all, the overdrive itself isn't original so why try to re-create an original kickdown switch. I used an o.d. kickdown plunger pushbutton switch from Jeepsterman in New Jersey and drilled a hole in the floorboard. In the end, I super-glued some pennies to the underside of the accelerator pedal to give me just the right adjustment.



The solenoid would not, indeed, disengage under load. That is why the solenoid has an extra terminal for a wire that runs to the side of the distributor. When you hit the kickdown switch it activates the solenoid which momentarily grounds the extra terminal (and the distributor). The engine dies for a split second until the solenoid plunger pulls out (or pushes in; the action is opposite on the 1940 from other years). This relieves pressure and allows the solenoid to move.