Checking Drive Shaft Alignment

The outer edges of the shafts must be compared to check the alignment of the front and rear drive shaft centerlines. If necessary, the alignment of the drive shafts can be adjusted by moving the center bearing sideways.

1. Measure the drive shaft diameters at the points where the weights are shown suspended in Illustration 3 and subtract the smaller diameter from the larger diameter. Divide this number by 2 to determine the required offset.

2. Three separate 60" (1.5 m) lengths of plumb line with suitable weights at one end are required.





Wrap the three lines around the drive shaft so that all the lines hang from the same side of the drive shafts (Illustration 3) as follows:

^ Front - Behind the front universal joint.

^ Center - Behind the center bearing.

^ Rear - In front of the flexible coupling.

The lines should not cross balance weights or welds.

3. Once the lines and weights are hanging motionless from the drive shafts, an additional line should be stretched horizontally so it just contacts the two rear lines, and then held in this position.

NOTE:
Use care to ensure that the vertical lines are not disturbed by the horizontal line.

4. Measure the distance from the front vertical line to the horizontal line (Illustration 3) to determine the drive shaft offset.

NOTE:
The offset dimension must be recorded on the report form.

5. If the offset is not the same as the required offset value calculated on the previous page, the center bearing must be moved to correct the offset condition.

NOTE:
Record the distance that the center bearing needs to be moved to correct its position (error dimension). This equates to the measured distance minus the calculated distance.