To align the driveline, safely raise the car or truck by its axles and support it level, so the wheels and propeller turn while it is resting on the stands. Get rid of all external bearings or snap rings before you fit the inclinometer base to the shaft. Turn the shaft so the transmission/transfer case output yoke bearing cap is beneath the shaft and take all measurements at the front and the rear. Place the inclinometer so it is parallel to the shaft on the bear cap, center the bubble in the sight glass and record your results to obtain the Output or Transmission Yoke Angle. After that, rotate the propeller shaft by 90 degrees and mount the inclinometer parallel to the shaft on the yoke bearing cap, guiding the bubble to center so the reading shows the angle of the propeller shaft. The transmission output operating angle is found by subtracting the smaller value from the larger. You should then move the propeller shaft 90 degrees and lay the inclinometer on the pinion yoke bearing cap in line with the shaft, adjusting the bubble to center it and measure the angle. Subtract the smaller value from the larger one which gives you the axle Input Operating Angle. It is important that the operating angles of the U-joint are well canceled, are no more than 3° and that the propeller shaft has a continuous operating angle of at least 1/2 of a degree.