3 SPEED TRANSMISSION 1971 SPEEDOMETER GEAR CHART DRIVE GEARS 666 6 6 6666 I 6M666 66 I 6666666 DRIVEN GEARS 3987918 Brown 18 3987919 Natural 19 3987920 Blue 20 3987921 Red 21 NOTE To order speedometer gears and parts transmission type rear axle ratio and tire size must be known REAR n A AXLE REAR TIRE SIZE 4 337 GEAR 4 343 GEAR 4 329 RATIO SPEEDO DRIVEN SPEEDO DRIVE ADAPTER ASSY 2 733 G78 15 3987921 6261794 3950350 2 733 L78 15 3987920 6261794 3950350 3 083 E70 14 E78 14 3987920 6261794 3 083 F70 14 F78 14 F78 15 3987919 6261794 3 083 G70 15 678 15 H78 15 3987918 6261794 3 308 E78 14 F78 14 3987921 6261794 3 308 G78 14 3987920 6261794 3 364 E78 14 G78 14 3987921 6261794 1972 SPEEDOMETER GEAR CHART DRIVE GEARS Part I Number of Number Color Teeth 666 76 DRIVEN GEARS 3987918 1 Brown 18 3987919 Natural 19 3987920 Blue 20 3987921 Red 21 3987922 Solid Sliver 22 NOTE To order speedometer gears parts transmission type rear ax e ratio tire size must be known GM PARTS DIVISION GENERAL MOTORS CORPORATION CHEVROLET 11 4 000 GROUP 4 8 c REV 4 81