Hi,
I had that happen to a speedometer head on my 1978 many years ago.
It turns out, that over the many miles it had recorded, the gears must have gotten gummed up.
The gears or one gear gets to hard to turn on a shaft.
That gear either turns with the shaft or the pressure between the gears drives a shaft up out of its investment casted journal position.
The two jump apart from the drive gear that turns both shafts.
Consequently, one set of geared numbers on a shaft stops increasing in value.
On mine, at the time, I just center punched the metal around the shaft to hold the shaft down into its proper place.
If the whole speedometer quits, which actually happen first, check the cable housing on the transmission. In my case it cracked as something may have smacked it from the road.
The crack allowed the cable to slip out a wee bit to become disengaged from the drive gear segment.
I just put a zip wire tie around the whole housing to tighten it back together.
It been that way for the so many years, I cannot remember?
My speedometer shows 288k, of which I estimate, in between the two breakdowns, the mileage is short by close to 40 to 50k.
This car is my oldest now and a speedometer was low on a priority list during my young working years.
I have always had other kinds of “working” vehicles as back ups!
You know the squeaky wheels gets the grease!
Phil
Phil
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