Good info. I should have known that Jim would have a paper on this! From this, it looks like 5 degrees angular misalignment is acceptable (as lond as the shafts intersect in the center):
DESIGN BACKGROUND
The flex cplg serves several purposes:
First, it isolates and greatly reduces steering system and engine compartment noise from entering the driver compartment.
Second, the rubber disc provides vibration isolation from harsh tire and road feedback.
Third, the flex cplg is used to accommodate the design angle between the steering column and the steering gear input shaft (5 degrees maximum).
Fourth, the flex cplg takes up minor movement of the vehicle body relative to the frame.
Fifth, the flex cplg provides an electrical ground path for the horn.
I have seen flex cplgs that performed extremely well for over 100,000 miles as long as they were kept within their design limits and guidelines.
However, the flex cplg was not designed to take up misalignment between the gear and the column. Here is the difference. The angle between the gear and the column is the angle in which the theoretical column centerline and the steering gear input shaft centerline intersect. The intersection point of the column and the gear should be right in the middle of the flex cplg and should not exceed 5 degrees. Therefore, the laminated rubber disc flexes at the intersect angle.
A real problem arises if the column centerline and the gear input shaft centerline do not intersect. In other words the column doesn't point directly at the gear. Now the flex cplg has to stretch up, down, or to the side (as well as being placed at the design angle) just to attach the column to the gear. It is this stretching of the laminated rubber disc that quickly ends its useful life. Furthermore this misalignment causes the steering column flange to continually contact and wear through the stop pins. Misalignment also puts a very high stress on the steering column lower bearing.
Glad (cool) for once I can be of assistance rather than always taking.
