torque tube couplers OEM design

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every engineer knows that torque on a simple shaft will cause it to short axially.

However the GM guys that went with the couplers from Germany for our C5s didn't consider this for a 600 rwt application .

I have not been able to get a season out of the stock couplers so this time I looked at what was happening.

the pictures shows how the stock couplers permanently shorten the effective axial length of the propeller shaft by 5/16 inch. In my case you can see how only 3/16 of an inch was still on the bearing seat. It is suppose to have 1/2 inch. I could move the spline shaft in place and feel the play.
This causes an inordinate wear on the aluminum seat which cant be repaired.

with the new after market couplers the bearing now goes the 1/2 inch in and there is no play now. Time will tell if the new couplers last, they look more robust.

the OEM couples are placed together back to back to show the gross displacement.