I have a 1950 F1 flathead v8 with 3 on the tree. What is the "overdrive" under the dash actually supposed to do? and how should it function? Thanks.

 

Can you post a picture of your transmission?

 

If the other end of the cable is attached to a box at the end of your transmission extension, you probably have an OD. OD is a planetary / sun gear set that lowers the engine rpm about 30% for a given road speed. ODs of that era had a governor that prevented them from engaging at less than a road speed of about 26 mph. With the OD cable pushed in and the OD working the unit should shift into OD at speeds above 26 MPH when you leave off the throttle. When you depress the throttle all the way while in OD you make an electrical switch and the OD unit will shift out of OD and the power will be direct thru the unit.
I would consider the OD about the most desirable unit to have on these old vehicles if you drive it much. I've owned several vehicles with such OD unit and have installed several of such units to replace transmissions.
Go here for a previous discussion.
https://www.ford-trucks.com/forums/6...sion-work.html

 

The thing is, I and several other folks on here have contemplated putting an OD 3-sp in our 48-52 trucks, and all have concluded it would be near impossible to do -- the governor ends up right where the main crossmember is, and would likely even hit the brake master cylinder.

 

If you do have a complete OD - Here are three free books on the care and feeding of the BW Overdrive
Deve's Antique Chevy Truck Restorations | Borg Warner 3-Speed Overdrive Index

 

I've not looked into the installation of the OD into this vintage truck. All my experiences were with cars, 50 Ford and 53 Merc, back when they were DDs. And then there was my 52 Merc.
Anyone looked into installing the Volvo unit, forget what they call it, but I see them advertised on ebay.

 

That is the Laycock deNormanville unit. More compact but adapting the parent trans to a flatty or anything else would be a total custom job. I've had them on British cars, and they are very nice pieces. They operate completely differently than the B-W. They use a hydraulic pump operated off the output shaft of the trans to engage the planetary.

 

So my 1954 F100 decodes as having a 3-OD trans, which I am guessing means this truck had the OD from the factory. My grandfather bought it in '63 without an OD. I think it would be cool to put one back on it. How hard are these units to find, and anyone out there want to part with one?

 

F100PJ they are out there. I put a want ad on craigslist several years ago and found one in nearby CT for my 54/ 223 six. You need a shorter drive shaft as the tail shaft is longer than the stock three speed. Mine came with it. Believe I paid $250. Parts are for the most part, still available from VanPelt Services. My truck is aways from being road ready but driving this OD is one of the things I am looking forward to the most.

 

Explains the use of the Overdrive
1950 Ford Color Film Part 2 of 3 - YouTube

 

Super video! The part after the OD demonstration, about the impact of buying American, is something to remember.

 

there are 2 more videos to go with it. Vid 1 is about the proving grounds and part 3 is more on production. I like the instructions on the OD