Speedo strangeness....

[XS TORQ]

I have been seeing some strangeness from my speedo lately - at freeway speeds, the speedo is jumping up and down 10-15MPH, with no change in pedal modulation (or tach).
Any ideas/suggestions?
Thanks,

 

[-RUNNR]

Sounds like a broken cog

 

[99 R/T 10]

doesn't the speedo run off a digital(electronic) imput from the PCM?

 

[Jay Herbert]

I know on some of the older speedo's the damping fluid leaks out....... results are similar to what you mention..... where's the "speedo guy" when we need him?

 

[Jeff Torrey]

I propose that you do not have stock gears in your car. There is a speedo calibration box in your car under the dash, and It is malfunctioning. My car just did the same thing to me. The speedometer would not read over 70 mph, no matter how fast I would go. Then it would read 50 mph in park. Cost me $200.00 installed for a new box.