THE TUBEWORKS UNDERDRIVE IS A MUST FOR PROFESSIONAL OFF-ROAD TRUCKS. USING A TURBO 400 TRANSMISSION, THE UNDERDRIVE DECREASES THE RPM OF THE DRIVESHAFT WHICH ALLOWS THE RING AND PINION RATIO TO BE MUCH LOWER AND STRONGER. WHEN USING 37", 39", OR EVEN 42" TIRES, THE NEED FOR A HIGH FINAL DRIVE NUMBER IS CRUCIAL. THE UNDERDRIVE ALLOWS THE DRIVETRAIN TO USE A LOW RATIO SUCH AS A 4.11 RING AND PINION, AND CORRECTS IT TO A FINAL DRIVE RATIO SUCH AS A 5:83. DEPENDING ON MOTOR COMBINATION (AS WELL AS TOP SPEED PREFERENCE AND WHEEL SIZE) WE CAN SET YOU UP WITH THE PROPER PLANETARY RATIO AND REAR END COMBO FOR MAXIMUM TORQUE OR MPH.THIS UNIT WILL ALSO ALLOW A QUICK INTERCHANGE OF PLANETARY RATIOS FOR THOSE COMPETITORS THAT WISH TO HAVE A NUMERICALLY HIGH FINAL DRIVE RATIO FOR QUALIFYING SCENARIOS. IN A MATTER OF MINUTES THE FINAL DRIVE CAN GO FROM 5.43 TO 6.29 OR LOWER.PICTURED ON THIS UNDERDRIVE IS THE 8-RIB PULLEY THAT IS USED FOR ALTERNATOR APPLICATIONS.[PULLEY IS AN UPGRADE AND IS NOT INCLUDED IN PRICING. 8-RIB OR V-RIB STYLE PULLEYS ARE AVAILABLE.] EACH PLANETARY UNDERDRIVE IS LUBRICATED AND COOLED FROM THE TRANSMISSION.[THE MATH TO DETERMINE FINAL DRIVE IS AS FOLLOWS USING A 1.31 PLANET SET. (LOWEST RATIO)] 1.31 (PLANET RATIO) X 3.71 (R&P RATIO) = 4.86 (FINAL DRIVE RATIO)1.31 X 4.11 = 5.38 (FINAL DRIVE RATIO)1.31 X 4.29 = 5.61 (FINAL DRIVE)1.31 X 4.56 = 5.97 (FINAL DRIVE)[ THE MATH TO DETERMINE FINAL DRIVE IS AS FOLLOWS USING A 1.48 PLANET SET. (QUALIFYING RATIO)] 1.48 (PLANET RATIO) X 3.71 (R&P RATIO) = 5.49 (FINAL DRIVE RATIO)1.48 X 4.11 = 6.08 (FINAL DRIVE RATIO)1.48 X 4.29 = 6.34 (FINAL DRIVE RATIO)1.48 X 4.56 = 6.74 (FINAL DRIVE RATIO)[COMPLETE CHART] 1.56 X 3.79 = 5.911.56 X 4.11 = 6.411.56 X 4.29 = 6.691.56 X 4.56 = 7.111.48 X 3.79 = 5.611.48 X 4.11 = 6.081.48 X 4.29 = 6.351.48 X 4.56 = 6.751.41 X 3.79 = 5.341.41 X 4.11 = 5.801.41 X 4.29 = 6.051.41 X 4.56 = 6.431.37 X 3.79 = 5.191.37 X 4.11 = 5.631.37 X 4.29 = 5.881.37 X 4.56 = 6.251.34 X 3.79 = 5.081.34 X 4.11 = 5.511.34 X 4.29 = 5.751.34 X 4.56 = 6.111.31 X 3.79 = 4.961.31 X 4.11 = 5.381.31 X 4.29 = 5.621.31 X 4.56 = 5.97
