Plug in torque tube

[Ken/Alabama]

Noticed the torque tube on my 39 Zephyr has a plug in it just in front of the flange that bolts to the banjo housing at about the 8 o'clock position as veiwed from the front looking toward the rear axle. I know the Fords dont have it but all the Lincoln torque tubes that I have seen has them. I do know just about all the driveshaft couplers that I have seen from a Lincoln has wear in it. Could it be that the plug is there to add some oil in there for the coupling. Since the Lincolns have a seal at the pinion,no oil can go up the torque tube like a Ford,just a thought. If it were there to drain any oil that leaks in there from the rear why wouldnt it be located in the bottom at the 6o'clock position?