Fluctuating speedometer

[Scarub]

Hello all, long time T-bird enthusiast and new to the forum. Picked up a 64 a week and a half ago and the speedometer fluctuates between 10 mph when driving. Any ideas on what the cause could be? Do I need the speedo rebuilt?

 

[Darrellinceres]

Could be speedo or the cable. I've had a bad cable that would cause my gauge to jump like that. The cable would catch the broken half and flip it every revolution. It could also be the plastic gear into the tranny. I'd check the easier stuff before I pulled the dash apart. I haven't had to deal with any dash problems on my bird yet. This is what I've seen on other cars I've had.

 

[tbird5866]

No need to pull the dash apart... Remove the bezel and three screws to remove speedometer from instrument panel.