How Did This Happen? Bent Speedo Needle and Broken Cable

[Margos Dezirian]

When I got my 66 300 the speedo was stuck on 53 mph.
I decided to look at that today.
The needle was bent and as unable to move.
You can see where it abraded the backing past 110 until the end
The cable was broken off in the transmission pinion.
Even after straightening it as best I could it was nowhere near 0 MPH at rest.
I straightened the needle an reclocked it.
We'll see if it's accurate when I get a new cable.
Can anyone conceive of any way this could have happened?
I have buried speedos in other cars in the past but never broke anything.

Also put dimmable LEDs in for the dash lights. WOW!

 

[CBODY67]

Look at what the needle attaches to (the speed cup) and see if it moves freely. Then look at where the cable attaches to the inner speed cup (sticks into it). There should be no touching of those two cups. But there is a plastic (usually) bushing that the inner speed cup rotates in. See if it is still in good condition. Also look at the clock spring that is attached to the speedometer needle, which should return it to "0" and such.

If the speedometer cable snapped-off in the transmission in the speedometer driven gear, that means that something up top-side stopped turning as the car was in motion. Which could mean an inner piece of the speedometer cable housing came apart internally and stopped things very quickly or the two speed cups touched long enough to spin the needle to the "max travel" position and then the cable broke. Snapping the clock-spring in the process. But that touching would have made a loud scraping noise, too. And would have had to be stout enough long enough to break the cable at the driven gear.

Your task is to look for what caused everything to lock up. Look for mis-alignment of the two speed cups, and the condition of the inner speed cup bushing. Then go from there.
Something got out of whack, no doubt.

The other task will be to find a source for a new speedometer cable assy. One already made up and ready to install, as the original was. Not a universal cut-to-fit item (as many sources will now sell). Then inspect the driven and drive gears for damage. The FSM tells how to remove them. www.mymopar.com

Hope this might help.
CBODY67

 

[Margos Dezirian]

Thanks, your reply is appreciated. I will have to look harder at the bushings.
It looks like the speed cups are pretty light aluminum. Hard to imagine that they wouldn't show some damage from stopping and breaking the steel cable. The clock spring is pretty light too and is intact.
there is some wobble in the inner cup that the needle shft attahes too and the odometers seem to be functional.
i will know more once I find a speedo cable and drive it.

 

[Toolmanmike]

Sometimes cable cores will catch and wind up and all of a sudden let go. That sends the needle into the stratosphere and bends it up.

 

[Margos Dezirian]

That sounds like a good theory.

 

[SuperDave]

If it were me, I'd test it first before installing. Obviously it'll need a new cable, something you can get at RockAuto. That's where I got mine anyways. Insert the cable into the speedo head & spin the trans end by hand, then with a drill. That'll show if it's viable to be reused and installed, or if you have to source another one.

 

[CBODY67]

Was the cable you got a "universal fit", within a range of cable lengths, item or was it ready to install, being more "application specific"?

Just curious,
CBODY67

 

[Mopar2ya]

You went too damn fast!!!!¡