My 56 F-250 came new with the heavy duty 3 speed transmission. When I shop for an overdrive for this transmission, will I have to look for an overdrive unit that is specifically made to fit the 3HD transmission? Alanco, you mentioned the -11 vs. -10 casting code. I'm not familiar with that, or where to find it.

 

I am not aware of any difference in the overdrives, only the transmissions. The Borg-Warner overdrives only fit Borg-Warner transmissions, and because the truck boxes for Fords have a longer, larger main drive gear/input shaft, it is easier to put an overdrive on a truck box that is from a passenger car. They are strong enough for most purposes with an F-250. The mention of code 11 cases came from another poster. Since you have a 56, you need a 12V solenoid for the OD. The governor is only a switch, and the OD relay needs to be 12V.

Regards,

Alanco

 

Thanks Alanco! All great info, but brings more questions to mind too.

Sounds like a BW overdrive out of most 50's Ford cars and trucks would work on our BW truck tranny. Anybody know how far into the 1960's that interchange holds true?

I guess I'm trying to figure out how large the field is for potential donor vehicles, and be able to ask the right questions at the wrecking yards.

 

Overdrive generally ended being used about 1966 or so. It was used in Galaxies and Fairlanes.

Alanco

 

I learned about OD's on my dad's '67 Country Squire, so they went at least that far.

I'd struggle to find where I saw the info on the casting numbers, but the jist of the article was that there were two distinct "grades" of OD's and one was stronger. It came up because someone was trying to swap internals and they didn't fit. My notes say the casting numbers are R10-x and R11-x. Could also be there was a non-Ford version, as IH and Studebaker used them in their trucks.

Edit: I did a websearch and found this fascinating collection of truck-related ads -- hit the arrows at the top of the frame to navigate forward/backward!
http://www.usgennet.org/usa/ar/count...-overdriv.html