Mike,

I would emphasize Otto's 2nd question above.

Did you rebuild/replace the speedometer itself? An original unrestored speedometer is going to have decades old lube that is more like a gummy/sticky consistency which could cause the results your are describing.

More thoughts and ideas once you can let us know some answers to these questions.

Dan


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)