40 Speedo to open driveline

[Pech33]

I am contemplating a chassis switch due to rust issues in critical places on the frame on my 40 convertible. In looking at the issues, the speedometer gear is in the enclosed driveline. Is there an adapter for the speedo if I want to keep the original 40 three speed mated to an open driveline to a Ford 9" differential. If not, how do you get the speedo to work?

Any thoughts?

[V8COOPMAN]

Originally Posted by Pech33

I am contemplating a chassis switch due to rust issues in critical places on the frame on my 40 convertible. In looking at the issues, the speedometer gear is in the enclosed driveline. Is there an adapter for the speedo if I want to keep the original 40 three speed mated to an open driveline to a Ford 9" differential. If not, how do you get the speedo to work?

Any thoughts?

It's all going to depend on what type of transmission you intend to run. If you are going to stay with a flathead and three-speed trans, there is an open drive version that was used in '42 and subsequent pick-up trucks, which has provision for the speedo cable at the rear of trans. Otherwise, if you end-up using a T5, or a Muncie, or any of the Tremec 5-speed overdrive transmissions, most have the mechanical speedo drive which most times, hooks right-up to the old Ford speedo cable.

You're going to have more trouble getting the registration paperwork sorted out, because with a new chassis, you will lose the factory-stamped serial number on the left frame rail. There are ways to 'fake' it, but the State motor vehicle folks are smart now-a-days. And if you ever have an insurance claim, THEY'll find-out and refuse to pay. DD

[19Fordy]

Here are the open driveline conversion parts if you plan to keep the stock 3 speed transmission.
https://www.fordbarn.com/forum/showt...ine+conversion

[V8COOPMAN]

.

This is basically the transmission you end-up with using "19Fordy's" pieces (ABOVE) ....an open drive three-speed Ford trans. DD

[Pech33]

Excellent. Thanks for the info. I am going to have VanPelt rebuild the original 40 trans with these specifications. You saved me a lot of investigation.

[Pech33]

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19Fordy: Do you still have those parts for sale?

[Offy 220]

Pech33,
Years ago [late 1970's] I did the same setup you are asking about in my '40 coupe - Ford 3 speed side shift transmission with the "truck open drive line." The stock Truck rear transmission mount is 8" on centers and the stock 1940 rear mount on a stock 1940 frame is 10" on centers.

I made these two "adapters" using the stock Ford donuts and machined collars to locate the adapters on the frame mount. You will have to purchase a GM PowerGuide rear yoke or after-market. The output spline on the truck shaft is the same spline as the PowerGuide yoke. As I said, I made this setup years ago so someone may have a better idea. Mac VanPelt's transmission booklet has information regarding this and part numbers you will need.

[Offy 220]

Pech33,
Here are a few photos of the adapters and transmission yoke. If you need any other information please let me know.
Offy 220 [Bruce]

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[Pech33]

Thanks Bruce. Great info to have to make my decision. I can keep the banjo or swap it out, it depends on how much I want “to open the jar”! One thing leads to another, it always does. Pat

[Pech33]

Are there any issues with alignment of the driveline if I keep the Banjo and convert the transmission to an open driveline connection? Anything else to consider?

[V8COOPMAN]

Originally Posted by Pech33

Are there any issues with alignment of the driveline if I keep the Banjo and convert the transmission to an open driveline connection? Anything else to consider?

Yup! Without the torque tube and radius rods (once you've converted to open drive), what do you reckon will hold that banjo rear end solid with the chassis, or in line with anything like STRAIGHT? You now essentially have a rear end attached to the vehicle by one spindly, transverse-mounted spring. You need to have realistic and thoughtfully-engineered reasons for changes, rather than just dreaming stuff that you "might do"!. DD

[Pech33]

That's where the parallel leaf springs and shocks come in, correct?

[19Fordy]

Pech33: V8 has offered "Golden" advice. You will need to install a torque arm unless you switch to parallel spring set up. Read all this:
https://www.fordbarn.com/forum/showthread.php?t=115973