Hi, new to the forum. I recently purchased a '71 f-100, figured I'd fix the speedo problem it had at a later point, price was only 500 bones. I get under there to see what I'm gonna need for parts, & I find no provision for the cable. Truck started out with a three on the tree, but someone replaced it with a four with the non synchro compound low gear. It seems logical to me that the person who did the work cobbled parts together from two different trannies, probably a 2wd & a 4wd unit. Anyone else run into this? I did a forum search & didn't find what i needed. Seems like someone would be building an electronic aftermarket setup with a hall effect triggering collar you could clamp onto the driveshaft. any ideas/suggestions? Meantime, I can just hang an hour-meter on it. Engine is a 360.

 

Welcome to FTE

The speedometer cable attaches to the left (drivers) side of the output shaft bearing retainer on the New Process 435 4 speed.

That retainer has to be there. It's possible someone plugged the hole with a freeze plug.

 

The transmission is probably from an F250 4x4 with a divorced transfer case. Those have a boss cast into the tailshaft for the speedo, but it's not cut out and the output shaft doesn't have a gear on it, just a spacer.
You can get a electronically controlled speedometer from Summit, but then you're changing the whole instrument cluster and you still need to set up a pickup system.

 

You could find the tail housing from a 2wd trans. It swaps out bolt for bolt.