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If the OD is of the type commonly used on cars of that era, it should not affect the speedometer. OD cars typically had a different (lower speed) axle ratio than the regular drive cars. Your car may have mixed parts. Speedometer error can usually be corrected by changing the speedometer drive gear.

No idea what type OD was installed since 38 never had one and having a Super eight, it may even be an aftermarket unit. In 39 they offered the R6 which is called a semi automatic unit and is controlled by a centrifugal clutch which put the unit into OD when the clutch automatically engages it at a certain speed. Electric portion was mainly used to kick it out of OD if you wanted a burst of power. 40 on had full electric units and most trans and ODs thru 50 can be installed on the earlier regular engine cars.

On the speedo issue, cars with an OD unit typically had a different rear axle and speedometer drive gear had a tooth count correct for that axle. If they just added an OD and kept the original axle it sounds like the gear may be the wrong one for the axle in the car.

If it has an indicator light it may have been a typical Borg-Warmer R9 unit which Packard used from 40 to mid 48. When the knob is pulled out OD is completely locked out. When knob is pushed all the way in then it is mechanically and electrically able to have OD engage when the car reaches a speed of around 20 mph and governor enables the electric side to prepare the solenoid for engagement. In the R9 with indicator light, at speed the light comes on as a signal you can go into OD at any time. By releasing your foot from the accelerator briefly to lower engine torque and car speed a tiny bit, things move in the OD unit and the solenoid can finish moving the plunger in to place the unit in OD. As soon as the solenoid is fully engaged and unit is in OD the light will go out.

Once in OD, to kick down accelerator is pushed all the way to floor, kickdown occurs and car drops into conventional gear. You can then pass a car at full power or if OD is no longer wanted, pull the knob out to lock out OD. If just passing a car, as long as car is still moving above speed it will go back into OD when you let your foot off accelerator again.

The overdrive is for not original, but I'm not sure of the type. From the information I could find, the name I mentioned before (Lloyd Young) was a guy who specialized in installing overdrive in vintage cars that didn't originally have them.

I've attached pictures of the controls on the steering, as well as the unit itself. It is mounted immediately before the rear axle. Maybe someone will recognize it.

-Kevin

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  Overdrive control.jpg (150.85 KB)


  Overdrive unit.jpg (184.50 KB)

That overdrive is the back half of some 40s-50s overdrive trans that has been fitted with adapter plates and bearings to suit. Since there is only a ground and power cable to it along with the lockout cable I surmise it will work thusly:

Push the lockout knob in. That makes the overdrive available. When you get up to cruising speed, press the little button to the left of your column. That should turn the solenoid and I guess that little red light on. Then lift your foot off the gas a second. It should drop into overdrive. As you slow down, you will have to turn it back off as there is no governor to accomplish that and then the car will freewheel.

To back up you MUST, and I mean MUST turn it off and pull out the lockout knob. Normally that lockout is accomplished internal to the trans but since the overdrive is now independent of the trans, you must do it.

I believe that is correct.
(If you manually apply power to the solenoid, it will go into OD any time the car moves forward and torque is not applied to the driveline. When power is cut off to the solenoid, it will drop out of OD and freewheel any time the car is moving forward with no torque on the driveline.
It must be out of overdrive anytime the car moves backward.

I think it's easy to connect the governor (if present) to the circuit you have. But you'd still have to manually
lock out OD to back up, or even roll backward.
It might be easy to connect a switch to the gearshift linkage that would kill the ignition if the OD was not locked out when the car is shifted to reverse.

Thank you both. I realized that problem with reverse and OD a few weeks ago. I went to back out the car, and nothing happened. It took me a second to realize that the overdrive knob had been pushed in, probably from kids getting into the car. Pulled the knob out and worked fine.

I'll mess around with it this coming week to see if I can figure out how it works.

-Kevin

That almost looks like it could be a Gear Vendors unit. The Gear Vendors website is not very helpful as far as showing actual bare photos of their units but there is a photo of a universal torque tube OD that is installed inline much as yours was. Main difference is the open drive shaft in front but since it is listed as universal maybe there are options in that respect. If you can find a brand on the unit maybe you could also find documentation.

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That is a scary thought if you are as absent minded as I am. I could almost guarantee that step would be forgotten more than once if I had a car that depended on me remembering to do it. I guess not being able to reverse is a good indication something was forgotten but not convenient at some times or if in an emergency situation and you suddenly needed to back up.

Believe your transmission has the provision for a reverse light switch actuated by the moving shift rail. If the resistance from the knob and its cable is not excessive wonder if it would be possible to adapt something to utilize that shift rail action. A push pull cable might be able to be mounted so the rail could push against the cable end and have the other end move the lockout lever out of OD when going into reverse. You could also utilize something like the reverse lockout safety switch Packard added to the R9 to cut off the power to the solenoid and also drop it out when the cable was actuated. You would still need to manually push the dash knob in to go back into OD and reset but at least that would be a deliberate step and not likely need to be done in an emergency situation. If that manual knob action is hard to do then another cable is maybe not an option unless something could be done to lessen any resistance. In a high resistance situation something might be able to be done electrically with another solenoid to move the lever but still utilize the shift rail action to actuate the solenoid.

As long as the push pull cable end or the solenoid plunger was attached to the lever, when the dash knob is pushed in cable or solenoid would move along and be reset ready for the next time reverse was selected. If the car already has a reverse light switch it should not be too difficult to figure out a way to accommodate both functions.

I started the Super up today to try and tune it better. I can hear the engine stumbling some, like a miss, and the engine shakes some. It definitely does not run as smoothly as it should, and perhaps even a lack of power.

The timing marks on the timing light are jumping all over with the engine running at 600 RPM. I can't get it to go lower.
I'm unable to get a reading and have no idea where to set the distributor.

Is this a sign of a worn distributor? If the distributor needs a rebuild, how do I do that?

-Kevin

It could be one or more of several issues with the distributor. If the timing is jumping around at 600 RPM or so with a good timing light, It could indicate that the distributor cam needs cleaned and lubricated. Or there might be a problem with the springs in the mechanical advance unit. The ignition point spring tension might be low. A very loose distributor shaft bushing might cause it. If the engine has a vacuum leak or valve issues, the vacuum advance might cause the timing to float. A bad condenser might cause erratic coil firing. If you have a dual point distributor, there might be issues peculiar to dual point units. I have no experience with them to draw on. The distributor rotor might be loose on the shaft. Plug wires leaking or cross-firing could cause erratic firing.

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Not a dual-point distributor thankfully. Plug wires are all new and I routed them so they don't cross each other and do not contact anything metal, just in case.

I checked for vacuum leaks with carb spray around everywhere I could think of. No noticeable change to the sound and speed of the engine. Valves were adjusted with the engine out of the car. They have not been adjusted since running the car.

Coil, condenser, points, cap, rotor, wires, and plugs are all new. So unless one of those components is bad out of the box it shouldn't be due to those.

How would I check the distributor cam and bushings? Maybe the problem lies there?

I'm assuming the timing light is good. It's new but just an inexpensive one from Harbor Freight. When pressing the trigger I can see plainly that the pattern of flashes is not consistent. It's quick, then slow, and it obviously is not steady. So it seems like something is causing #1 to fire erratically.

-Kevin