Stumped by Speedometer

[ThinLizzy13]

My truck is a 63 F100 with a 223 and three speed. I’ve had it for about 2 years, and before that my great uncle had it for about 30 years. For as long as I can remember the speedo was bouncy and the odometer was way off. I finally decided to fix it.

I pulled the tail shaft housing and the drive gear was toast, the driven gear was wrong for my tire size, and there was an old busted driven gear hanging out in the housing.

I installed a new drive gear and new driven gear. I then pulled the speedo cable and inspected. It looked good. I coated it in graphite and reinstalled. Still had a bouncy speedometer....

I then decided to go all new. Ordered a new speedometer cable and installed. Still a bouncy speedometer and an odometer that is way off

I’m at my wits end with this issue. Is it possible I have a bad speedometer in the dash? I cannot figure out what is causing the problem. Any ideas from more experienced slicksters?

[slick4x4]

I would say it's the speedometer gauge
Might solve with some lube sprayed in the back
Before you take it apart ...
You might take the cable out of the trans
Chuck it in a drill
Let somebody watch
the speedo while you spin it
If it bounces ... nothing wrong in the trans
If it's smooth ... might be a gear slipping

[ThinLizzy13]

I forgot to mention I had already tried that with both of my cables lol. Looks like be taking the speedo apart...

[slick4x4]

Before taking it apart
I would take the cable off
Get a good quality spray lubricant
Squirt it into where the cable goes

Might work ... won't take long to try

[ThinLizzy13]

I had been using graphite. Cleaned everything up really nice and hit it with WD40. Pulled the speedometer and gave some WD-40. Took it down the road. It does well up until about 30, but then it quivers. It’s off consistently by about 10mph, so I may also have miscalculated the driven gear.
I think I need to clean the speedometer up better and re-lube...

[ras4434]

I solved my speedometer problems forever. took out the gauge and cable and threw them in the trash. Bought a GPS gauge and sender from Speedhut and with three wires have never had a problem....although now I have now excuse for knowing how fast I am going. Love it.

[jercasche]

I bought an Auto Meter GPS speedometer and love it. The only downside is that it takes about a minute to link up and give you a speed reading. I kept breaking speedometer cables on my old factory setup and it also jumped all over the place as well.