I own a 39 Packard 120 sedan with overdrive. Can someone explain to me how the overdrive operates and the way it feels when you are driving the car with it on or off. I have the cable with the knob but when I push it or pull it there is no difference in how the car performs. The cable is moving at the transmission. It may be electrical but I am not sure. HELP!!<BR>Thanks,<BR>Arend

Not familiar with that overdrive tranny; however on the two overdrive units I do have (Borg Warner), they both are set for overdrive when the lever or handle is pushed all the way in. About 28-32 mph, a letting off the accelerator causes the overdrive to kick in. One one car it is noticeable while the other more subtle, but definitely obvious. Does your have a relay? On mine there are relays (on the firewall) and these have a fuse mounted with them. Also mine have four wires that connect from the relay to other points for the operation. Hope this helps a little until someone with a model like yours comes aboard.

According to my Motor Book, the 1939 is a semi-electrical system that uses a relay and solenoid. The soleniod appears to have 2 wires and is mounted on the side of the overdrive unit. Apparently there are 2 different versions, and early and late 39. The difference being the late 39 uses a reverse lockout switch and is wired through the ammeter and the early does not use these two components. Both use a relay.<P>Sorry I don't have a scanner otherwise I would copy the diagrams.

I want to thank both of you guys for responding to my question. I am going to go to the libary and get a copy of the Motors manual for the car and maybe it will help. It must be electrical because the cable is free and does push and pull correctly. I will keep everyone posted.<BR>Thanks,<BR>Arend

[JT]

The wiring change Chris mentioned started with engine no.B318799A. If you have the reverse lockout switch either it or the kick down down switch will energize the solenoid and disingage the overdrive. Both the solenoid and relay are rebuildable if that's where your problem is. <BR>Have you checked the control cable to make sure the lever has full travel? You should have some clearance between the stop and the knob when engaged so it doesn't bottom out when pushed in. You could disconnect cable from lever on overdrive and check that it is fully toward rear of car (engaged).

The relays on my Studebaker and Kaiser models have a 25-amp fuse mounted on the front of the relay; however I have seen some with the fuse almost hidden underneath. And IF the relay is old, it is entirely possible that one of the plug-on terminals may have become desoldered and loose and thus not making contact.

I am not sure the library will have the Motor Book. Mine is from 1952.

REGARDING OVER-DRIVES<P>ALL of you guys are correct - as far as you went. Let's discuss WHAT those early over-drives did, and HOW they work.<P>The dash lever when pulled OUT, should lock out the entire system. All electrical and mechanical components of the overdrive are locked OUT. The car will be locked in direct drive. The typical final drive ratio of those years is WAY too low for normal highway driving today - at 55 mph your engine will be spinning FASTER than a modern car would be at over 100 mph. DO THE MATH !<P>When the dash leaver is pushed IN, the over-drive functions take hold.<P>The most dramatic MECHANICAL difference is that you are now in "free wheeling" - easy to tell if that MECHANICAL portion of the system is working, because if you take your foot off the gas to "coast", there will be no "engine braking".<P>At somewhere around 22 mph (depending on what version of over-drive, and the car's final drive (axle) ratio, the over-drive will "cut in", so long as the gas pedal is not more than about 1/2 down (most people "sense" when the over-drive is about to cut in, and take their foot off the gas during the "lock up")<P>You will know when you are in over-drive, because the car essentially shifts into a <BR>fourth gear. THAT gear is SO much higher than the "third" or "direct" gear, you will think you are in a whole different car, because "in over-drive", your motor will be loafing even at extreme speeds. To give you an idea, the typical over-drive equipped car in its DIRECT drive will be doing around 3,000 rpm at 60 mph, but in "over-drive", the motor will be spinning around 1900 rpm...<P>So - there you are...that is how it WORKS as felt by the driver. If anyone wants a further discussion on how it works mechanically and electrically, let me know.<P>Pete Hartmann<BR>Big Springs, AZ

'Freewheeling' ?????? The only freewheeling i am aware of has NOTHING to do with overdrive but rather with the CLUTCH mechanism of a std shift. When the gas pedal is released a vacuum belows pulls the CLUTCH disengaged. This is independent of any overdrive AND was available without o'drive. DO the O'drives offer a Nuetral position of something that i am not aware of? ?????

[JT]

Yes, the overdrive when engaged allows the car to freewheel. I believe the 39 model has a higher cut in speed than the later models although it is adjustable with a pawl adjusting screw on top of the OD unit. The 40 and later models require changing the governor to change the cut in speed.