Drive shafts are found in many rear-wheel drive cars and trucks. Shortening or modifying a drive shaft may become necessary if the vehicle has a different motor or transmission than it came from the factory with or some other modification affecting drive line length. Shortening the drive shaft can be done by most experienced enthusiasts and "shade tree" mechanics if you have the right tools, but be aware that this is a precision modification. If you are not sure you can complete the modification, take the shaft to a qualified shop.
Use a tape measure to be certain of the needed length and mark the drive shaft with tape at the cut line to indicate the amount you need to shorten it. Check your measurements. Once you cut it, there is no going back.
Cut the tubing of the drive shaft with a cutoff saw (sometime called a chop saw), being sure to keep the drive shaft square to the cutting wheel. Clamp the shaft down to be sure it doesn't move.
Remove the splined section of the drive shaft from the tubing by grinding around the end of the tubing or cutting with a lathe. The splined section will separate when enough material has been removed around the end of the tube.
Discard the short section of tube you cut off and clean up the edges of the splined section where it will slide into the remaining drive shaft tube. Do not grind off material or it may not fit tightly into the drive shaft
Clean up the cut edge of the remaining drive shaft section with a die grinder or angle grinder. You only want to remove burrs and not remove too much material, or the sections may not fit snugly when assembled.
Insert the splined section you removed from the cut section of drive shaft into the tubing of the remaining drive shaft. You may need to use a dead blow hammer to ensure the two pieces fit completely together.
Align the two pieces and turn them in a lathe (very slowly) to check for run out and to be sure they are square. If they are not, continue to adjust the angle at which the splined section and the drive shaft are joined until the assembly runs true. This is critical as it is a spinning assembly and vibration can cause damage to the rear end, transmission, and other parts of the vehicle if the new shaft wobbles.
Weld the two pieces together using an MIG welder. Work slowly so you don't warp the metal or cause a weak spot that could fail later.
Clean and paint the new drive shaft. Install it into the vehicle and road-test.
