Speedometer Problem - 1966 Pontiac

[sppingel]

So I was driving my 1966 Pontiac today and the speedometer went haywire. I know some people on this forum are familiar with 1960s cars to I came here before I messed with it.

 

I was going 25mph. The speedo shot up to 50, then to 0 and stayed at 0. During the next 10 or so miles it would randomly tick up to about 10mph while I was crusing at 45mph then fell back to 0.

 

Are these things 100% mechanical or are there some electronics involved? I know there is a cable but I don't think it snapped because it ticked every now and again. Where should I start?

 

Oh the odometer still works.

[txab]

100% mechanical

[hockeypro1411]

Hm. I'd guess it's something on the actual gauge side. I know on older trucks (the same may apply for cars, but I'm not sure) you could unplug the speed sensor from the transmission to stop the odometer from turning, but you'd lose the speedo. The fact that the needle still flicks around is why I'd start at the gauge itself.

[desrtrat]

sounds like your cable is going out. after 44 years i think you got your moneys worth..

remove the cable from the trans, and the speedometer head and see if the cable is fraid at the ends, most common places for failure. on some of the older ones you can pull the cable out of the housing and just replace it, and reinstall it back in the housing. if you can, when replacing it coat the cable with some white lithium grease will keep it quite. also check the key way on the trans and head for damage. check the speedometer gear in the trans. another sores of failure..BTW- you still running a power glide??

 

good luck, hope this helps

 

[Doug_Scott]

if the odometer is still as accurate as before it will be in the speedo head itself. The odometer is direct driven off the cable, the speedometer is just a C shaped piece of metal with a magnet on the ends spinning around a what can be best described as a disc (actually sort of frost plug shaped). If the odometer is accurate, then the cable is spinning the correct speed and driving the odometer. The speedo part may just be dirty. Does not take much to interfere with the magetic portion.

[sppingel]

It is the original th400. Awesome tranny in my opinion. Although my dad told me that the fastest car he has driven was a 66 or 67 GTO with the 2 speed powerglide.

 

I took it around the block today and the speedo worked normally for about a minute. I'm going to pull the cable off and see what everything looks like. I might as well get a new cable though while I'm at it...

[team3-8]

That Catalina is beautiful!!! My dad had a 389 4bbl 66 catalina 4 door when I was sixteen, that car would rip the tires loose and cruise the highway like floating on a cloud. Loved it. Sweet Poncho you got! Post more pics.