My 1966 f100 is sitting on a 79 f150 frame, it has a C6 transmission. Will the speedometer cable screw right into the 66 dash? Or are there different ends that are needed?

 

1961/72: The cable threads into the back of the speedometer.

1973/79: The cable is retained to the speedometer w/a clip.

 

One end is already connected to the transmission, it has a retaining clip. The other end looks like the image on the left. Does that look right?

 

Seems OK from here. The back of the sweep speedometer is a threaded connection. If I put calipers across the threads it is 5/8".



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Cool! Thanks for the info and pics guys.

 

The clip retains the nylon speedometer DRIVEN gear to the cable.

 

This is similar to the connection on the transmission. The other end has a threaded ferrule. NumberDummy, you are saying I am missing a plastic clip, that clips on the ferrule and back of speedometer?

 

This supposed to be a 1966 speedometer cable. I only see a grommet. Am I missing something here NummberDummy?

 

I read your post again. Sometimes, I'am so stupid. Argh!

 

So guys, It threaded right on. Took it for a spin and the needle pegs out.Do I need a different gear on the transmission side? Do I need a custom cable? Thanks for your help.

 

Isn't your cable connected to the transfer case?

 

53deere, you are correct! Uhm! Had to go look.

 

The speedometer cable itself turns - from end to end - in a 1-to-1 ratio. Meaning for every rotation at the transmission/transfer case end it will rotate one time at the speedometer head. This is always the case. The way that the speed of rotation is changed is by using different driven and drive gears at the transmission/transfer case end. There are no changes at the speedometer head itself, only underneath at the lower end. If you pull the cable out there are gears behind it that can be swapped out.

In some cases manufacturers also used small ratio changing boxes that screwed to the outside, too. Here's one example with a quick search of a GM product that changes the ratio by a factor of 1.3-to-1. This is separate from the driven and drive gears which provide for some variations. Just an example of what they sometimes did. The right (wrong?) combination of rear-end gear ratios, transmission/transfer case and tires can make for some interesting approaches over the years.

CUCV / GM TRANSMISSION SPEEDOMETER CABLE DRIVE ADAPTER 1.3 RATIO TRUCK [C4S4] | eBay

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TA455HO,Have I jacked my speedometer already? It pegged out immediately!I wonder if anyone knows the correct gear for this? 1979 f150, C6 4x4 to the original 1966 f100 speedometer.

 

If you go very slow and it is pegged at 100 MPH or higher then no amount of gearing changes would solve that, I wouldn't think. Not sure what might cause that other than the speedometer head itself, perhaps, but that's just a guess.

Chad

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