1966 Pontiac Fullsize Speedometer Gear Usage

Information supplied by George Pearson
1966 Fullsize Speedometer Gear usage Chart
  Driven Gear Or Sleeve Tire Size Speedometer Adapter  
Rear End Ratio Part # Teeth Color 8.25 x 14 8.55 x 14 8.45 X 15 8.15 X 5 Model Ratio Part # Color Fitting & Seal Assy
4.11 9780522 18 GREEN X** X   X 6660-AJ .9705 9777006 RED 3869914
4.11 9780523 17 BLACK     X   6660-AJ .9705 9777006 RED 3869914
3.55 3860344 21 RED X X   X         3869912
3.55 3987920 20 BLUE     X           3869912
3.73 3860342 19 NATURAL X X   X 666-AJ .8653 9775436 BLUE 3869912
3.73 3860344 21 RED     X           3869912
3.42 3987920 20 BLUE X X   X         3869912
3.42 3860342 19 NATURAL     X***   6660-AJ .9705 9777006 RED 3869912
3.23 3860342 19 NATURAL X X   X         3869912
3.23 3860341 18 BROWN     X***   6660-AJ .9705 9777006 RED 3869912
NOTE: X** = ADAPTER REQUIRED WITH POLICE OPTION
NOTE: X*** = ADAPTER REQUIRED
Information supplied by George Pearson, taken from a Pontiac Parts Book