If driveshaft is suspected of being out of balance, check for missing balance weights, broken welds and any build up of dirt or paint that could cause the driveshaft balance to be affected.
Inspect U-Joint and clamps for wear or looseness, replace if required. If the driveshaft is bent, it will have to be replaced.
To field balance a driveshaft, raise vehicle parallel to the ground so that the vehicle can be started and the tires and wheels can rotate freely.
Measure about six inches from the yoke end, and place four marks 90 degrees apart around the driveshaft. Number them so that they can be identified.
Run vehicle and note vibration intensity and speed when vibration occurs. Place a screw type hose clamp at the first position. (See fig #1)
Run vehicle to see if vibration changed, if not rotate the clamp so the screw is at the next mark on the driveshaft.
If after positioning the clamp at all four positions, the vibration is not changed, the vibration may not be the driveshaft.
Run vehicle, repeat until vibration seems to be reduced. Install a second clamp test again to see if vibration is reduced. (See fig #2)
If second clamp causes an increase of vibration, separate the clamp screws about 1/2” (See fig #3), and repeat test. Increase distance until vibration is at the lowest.
Make sure the clamps are tight and bend the loose end so that the screw will not loosen.