Periodically lubricate any places where parts meet along the driveshaft.
Driveshafts are balanced on the ends, not in the middle. When the driveshaft is out of balance, you can correct it using an on-the-car strobe-type wheel balancer. Heavy spots are counterbalanced by installing hose clamps with the screw positioned on the opposite side of the heavy spot. The pinion nose end of the driveshaft is where most of the first order driveline vibrations come from. Driveshaft flanges are sometimes balanced. This is to compensate for runout created during manufacturing. Weights will either be on the front of the flange or the outside depending on whether the correction was for flange runout or differential balance. Runout on the flange is checked with a dial indicator. It is limited to 0.006” when there is no weight on the flange.
One end of the driveshaft is balanced first. After the other end is balanced, the first end is rechecked. A transducer is a good tool for testing for driveshaft imbalance. This is part of an on-the-car wheel balancer. It is mounted on the differential case, under the pinion gear.
A transducer is a magnet that is spring loaded on both sides. It moves back and forth in a coil of wire, sending a signal to a meter in response to vibration. The drive shaft is marked anywhere with a piece of chalk. When the driveshaft is spun at the speed where the vibration occurs, the transducer triggers a strobe light. When the light illuminates the mark at the same place (6 o'clock, for instance). At this position, the heavy spot on the driveshaft is on the bottom of the shaft.
Large hose clamps are positioned on the shaft opposite the heavy spot. Then, the shaft is spun again to see whether more clamps are needed to correct the problem. You can move the hose clamp to one side to see if the vibration improves. If is gets worse, try it in the other direction.
Driveshaft balance can also be checked without special instruments. First, put four numbers around the circumference of the driveshaft. Because imbalance can be related to runout, put the #1 mark at a point opposite to the amount of greatest runout. Put the clamp with the weight at the #1 position and run the shaft. Check to see if it feels better or worse. Then, move it to the #2 position and try it again. Try all four positions. You are trying to find out where to put the weight.
When you find the best position, move the hose clamp halfway between the numbers to see if the vibration improves. If it gets worse, try it the other direction. When you find the best position, add another hose clamp and repeat the procedure. The clamps can be separated to fine-tune the amount of weight needed.