If you are mechanically inclined and feel up to a challenge, modify your driveshafts by shortening them. You may require shorter driveshafts because you've replaced your transmission or are modifying a custom, high-performance car. The driveshaft converts the torque of your vehicle's engine into the rotation of several other components that lead to the car's smooth movement, so it is integral to your vehicle's operation. Only attempt this modification if you are a skilled mechanic.
Don safety goggles, gloves and a dust mask, if desired.
Measure the new length needed for your driveshafts. Measure from the centre of the rear universal joint to the edge of the transmission's tail piece. Subtract 1 inch. This is length you should cut your driveshafts.
Mark the universal yoke's position on the driveshaft. Snap a chalk line along the driveshaft from the centre of the front universal joint to the centre of the rear universal joint. This will make a line on the yoke and continue the line along the driveshaft, ensuring that you can place the yoke in the correct position after the shaft is cut.
Remove the rear yoke by cutting it with a grinder. Cut along the welded seam by turning the driveshaft and holding the grinder against the seam. Keep the cut as straight as possible. Set the yoke in a safe place.
Measure the driveshaft and mark the location of the cut. Cut the driveshaft with a saw, preferably a cut-off or chop saw. Precision is key with this cut, so use a vice if necessary to ensure a straight cut.
Retrieve the yoke. Place it inside the newly cut driveshaft, and line up the chalk lines. Push in the yoke until it seats fully. Weld it in place by rotating the driveshaft a complete 360 degrees as you weld.
Pay a machinist to balance the driveshaft for you to prevent vibrations while driving.
Driveshaft failure can lead to extreme car damage or personal injury. If you are not a professional mechanic, think twice about making this modification at home.