" . . . I had a local older mechanic tell me that the drive train gets its oil from the transmission. Is this true? If not how do you add oil to the drive train? . . . "
The entire drive train does not get all of its oil from the transmission. The u-joint/housing and transmission share the same gear oil. The rear end has its own, separate, gear oil.
A bad seal in the transmission end of the torque tube might result in transmission/u-joint oil getting back to the rear end.
The engine oil is lighter weight and completely isolated from the rest of the drive train (except through leaks, as described by 51 ashton.
Have you checked your Shop Manual or your Operators Manual for lubrication information?
